If it were me - I am wicked cheap - I would not install a new distributor first. I am almost positive that (as long as there is at least 10 VDC on the pink at all times) the coil is shot. The insulation on the windings has most likely been effected by overheating (whether it was the fire or not remains to be seen). Now it runs hot and that heat is radiated to the module which has been failing as well. But don't ruin a new one if there is any possibility that the coils/modules are being destroyed by some outside factor.
Go to the junkyard and grab a complete OEM distributor. You can probably pick one up for $25. Even if it's not what you want for a final set-up use it as a diagnostic tool. Stab it in and crank. If the engine fires right up...it was definitely an internal issue with the aftermarket Accel unit. But you will not have determined whether it was caused by something external. Drive the truck daily and time will tell you if something external to the Accel was causing it's internals to fail. If you get a good stock distributor (confirmed because the engine runs well from the get go), leave it in there while you do all the other jobs on your hit list. When everything is done - and if the stock distributor is still firing the engine as designed weeks later - pull it and stab your new aftermarket unit.
My point is this, if you feel something external to the Accel was causing it to degenerate and start eating modules and coils, don't replace it with another big money show distributor until you see a cheap OEM unit function for an extended time.
There are essentially only 4 external factors (that I know of) that will cause an operating HEI distributor to fail - or not generate a spark;
1. The power supplied to the primary side of the coil on the pink wire is less than 10 volts. That scenario will cause a weak spark and if the voltage is low enough kill the engine. But in this case, no harm - no foul, no damage is done to the any of the internals. All that is needed is the resumption of the power supply to normal voltage. This is usually due to a short to ground in the pink wire but also happens sometimes if an HEI system is used in an older truck and the resistor type wire for the coil feed is not removed and replaced with a normal lead.
2. Another (very rare) cause of no spark that is the result of something external - and which can also cause permanent damage - is improper grounding of the primary circuit. A poor path to ground for the coil and the module can weaken the spark and cause early failure. The ground path for the coil/module starts at one of the module hold down screws. From there it is into the casing, along the shaft's outer sleeve and down to the clamping plate. Through the plate, into the locking bolt and finally from the bolt threads into the engine block (which is assumed to be bonded to the battery negative).
3. Excessively high voltage in the primary power supply. This is really rare because it needs to spike over 18 VDC - don't even consider that.
4. Really bad plug wires that can cross feed the sparks between them. There is more on this below. Personally, I think it's an urban legend - I have seen HEI systems keep running (poorly) with cross-firing. When the wires are replaced - it's back to normal.
Everything else is internal to the distributor.
Here is some other info on mismatched coils/modules:
Coil Power
While a good performance module will make a big difference in a stock HEI, matching it with a performance coil allows the system to work as efficiently as possible. In fact, all the aftermarket ignition companies sell matched coil and module sets to ensure optimal ignition operation. Coil design is very much a dark art and would require a textbook-sized story to detail all the different variations on the theme. Suffice it to say, by decreasing internal coil resistance, it is possible to decrease the amount of time necessary to charge the coil so it can fire the next spark plug with maximum energy.
This is an important factor since all the ignition companies we spoke to stressed the idea of properly matching the coil and module. The best way to do this is to use the coil specified by the manufacturer for its specific module. For example, ACCEL offers a stock replacement and two different performance modules for the typical four-pin HEI. Each requires its own coil to create optimal ignition power. What this means is that you should not mix and match coils and modules. In one particular situation, we combined a stock replacement module with a Petronix coil and the engine just seemed to run flat—as if the ignition timing were retarded, even though it wasn’t. As soon as we replaced the stock module with the matched Petronix module, the engine instantly responded and was again crisp and fun to drive.
Later, we tried to duplicate this coil and module mismatch in a different vehicle, but we did not see the same results. We also tried several mismatches of coils and modules with no apparent differences in , idle emissions, or throttle response. However, it’s clear that the best plan for optimal ignition performance would be to use the factory-matched module and coil.
And their discussion of module failure:
The single most cause of HEI module failure is coil related. Number 1 is the in-cap coil "layer shorting" When this issue arises, the epoxy coil has overheated (common for those coils due to the epoxy being almost the worst heat transfer material known to man), and has the primary windings insulation compromised and/or just plain burned away from some or more of the windings. This allows the windings to come together, short circuiting the length they have to be to operate correctly. Resistance is changed for the adverse, and the coil just plain overworks the module to failure.
It isn't enough any more to simply resistance test an in-cap, or any other coil. Real world, powered up tests are the new way to get it done correctly. Stores such as Auto-Zone have special testers that run the coil and test it off the vehicle, and give accurate feedback as to the coil's real condition/health. Do not just rely on "ohm'ing" a coil, get it run/load tested.
Next, two different scenarios, both as deadly as the other.
A) The carbon brush is compromised, and/or installed incorrectly. The correct sequence is: cap, carbon brush with spring positioned upwards, then silicone heat transfer grease on both sides of the insulator, installed onto the spring, then, coil. If this method isn't done correctly, the distance from the end of the carbon brush to the rotor connector bar becomes excessive, resistance on the secondary side and primary side of the coil rises, heat becomes too high, and the module fails.
B) The ground strap that grounds the coil from one of the coil hold down screws to the center terminal in the cap either is dirty and/or corroded. This makes for added resistance, and that is...module heat. Failure will occur. Contrary to what some will say, if this bar isn't in place with an in-cap coil, the coil WILL NOT MAKE SPARK. This bar HAS to be in place for a coil in cap coil for it to make spark, Doesn't have to be there for a remote, off cap coil changeover.
B-2) The small black wire that comes out of the coil on the in-cap coils is the second part of the coil ground, and has to be connected to the coil yoke to work. This wire grounds through the coil yoke, to the ground strap, three prong connector on the cap and ground wire, to the body at the module mounting area. If this wire isn't connected, no spark.
Spark plug wires. An HEI requires a wire set that has these features, magnetic suppression, spiral, or "magna" core, and be of sufficient diameter to allow the spiral core to effectively shield the voltage running through the wire. That said, steel and copper wire aren't shielded as a rule, and shouldn't be used with any good HEI or better electronic ignition system. The reason we need to run this specialty wire type is that wires will leak if given the chance, and when that happens, the leakage, referred to as 'RF leakage" (radio frequency) and can cause wires to magnetically feed voltage to more than one spark plug at once. Feeding more than one plug at any one time overworks the module and coil, and failure can result, along with misfire, early/late fire and other tuning/performance issues/problems.
Contrary to what some will also say, low voltage, as in still using the resistor or a resistor wire, will not kill an HEI module,. It will make the overall spark weaker exponentially as volts are reduced. After a certain level of volt input lowering, the module will simply stop working from lack of volts, and the system will simply not idle. Once again, low volts will not harm an HEI module, it'll just stop malking spark when it gets to the point it can no longer run on what isn't there. Add volts, it will come back alive again.
HEI modules need two things to be happy, a good ground and insulating grease to stay as cool as possible.
Grounding is accomplished with the screws on some modules, others ground from their bottom pads. Some modules will have a steel ring at one of the holddown screw bosses on the module top, THIS is the ground for those type modules. Modules that don't have the ring ground through their metal back plates.
Excessive heat can also destroy modules. The grease used on the underside of an HEI module is special silicone based grease designed to transfer heat from one surace to another. IT IS NOT DI-ELECTRIC GREASE. Di-electric grease is used for other things electrical, and shouldn't be used on module to body interfaces. Also, the silicone greases that we need for modules are HEAT TRANSFER TYPES, NOT HEAT BARRIER TYPES. Obviously, barrier greases would retain heat at the module source, not help to cool them.
Electrical connections at the module terminals need to be kept clean, and tight. Corrosion isn't wanted there, nor are loose connects. That kind of issue causes resistance, which is heat, which is death to the modules. These terminal connects ARE the correct places for di-electric greases to be used.
Caps/rotors can also make for excessive resistance, and can also lead to module failure. We all have heard of HEI rotors with burn through under the contact springs. It happens, and when it does, resistance and heat will kill the modules, and coils as well, if a person has a great deal of luck. And, as ozone buildup accumulates on the rotor tip and wire terminals, resistance is raised, usually, this isn't a serious issue, but a copper terminal cap is mandatory for good cap health. Avoid aluminum terminal caps.
and the carb, distributor, battery, and starter have all been put on either during or since the engine swap. The age factor is why I'm planning to replace all the starting/charging wires (battery cables/clamps, ignition to starter wire, etc) since they aren't in the best shape. I'm also going to change the ground straps just as a matter of course, unless it's obvious they are fine (visually and with a meter).
