I have thought long and hard about swapping from tbi to carb. We did it on my brothers 88 suburban and I was going to do it to mine but I'm just going to exhaust all possibilities with my tbi first. But this is what you will need to do.
You need to separate all charging wires from ecu wires(starter,alternator,ignition,fuse panel wire ect.).
Then you need to remove distributor and intake, throttle body. Install new intake and carb. Set timing to btdc 0*. Install new distributor, plug wires.
Now in order for your temperature gauge to work you will need to have the single green wire hooked up on the driver cylinder head as factory. In order for your fuel pump(electric in tank) to work you will have to reuse the oil pressure switch on the top rear of the engine block[next to distributor]. In order for the oil pressure gauge to work you need to also have the oil pressure switch hooked up on the lower driver side of the block{next to manifold-single wire}
You need a switched 12v to distributor for the coil to work. Just splice off the factory plug from coil for that. Sorry don't remember what color wire that was.
You need to install a fuel pressure regulator with return somewhere on your fuel line to regulate pressure down to about 6 to 6 1/2psi. You will also need to install a torque converter lock up kit(if equipped with 700r4 like it should).
For the carburetor you will need a geometry kit for the T.V. cable to work correctly. If you don't do the T.V. Cable correctly it will be bad news for the transmission so make sure you buy the right one for the carb.
Main things you will need to do to accomplish this will be
1. H.E.I. Distributor
2. Geometry bracket kit for 700R4
3. Carburetor (your choice)
4. Torque converter lock-up kit
5. 4-barrel intake
6. H.E.I. Spark plug wires (get from a 85 1500 chevy)
7. Fuel pressure regulator with return (make sure it has a return!)
Now here's the thing, you can do without the torque converter lock up kit BUT it's not to good on the transmission. When we did my brothers we never installed one and his truck did fine without it. You can look it up on google also many people go without it. It's not wise but it can be done. Also don't try to bypass the electric fuel pump by using a mechanical because they do not have enough power to pull through the electric pump(we learned the hard way). If you do want mechanical that's fine because then you just buy a factory replacement for an 85 1500 chevy, but you will have to drop the tank to get the electric pump out. Do not try to run a fuel pressure regulator that doesn't have a return as it will burn up the electric fuel pump. Trust me we did it and that's why we put a mechanical and learned it won't pull through the electric pump well enough to keep the motor running. You can use just about any year of small block chevy plug wires as long as it's for an H.E.I. distributor. Reason I say 85 is because it's easy to remember.
Best fuel pressure regulator with return for a good price is Mallory 4309 $101
Best intake to use for the price is a Professional Products Cyclone $143 (they bolt right up to the center bolt heads as they are designed for just that and have the same size runners as a Edlebrock performer)
Me personally I would go with a TCI lock up kit as they are cheaper and have everything you need to do the task $89
I am an Edlebrock fan for carbs but that's my own opinion most are Holley people. Just make sure you get the Geometry kit for whatever carb you buy.
H.E.I. Distributor don't matter what year you get as long as it's an H.E.I. You could even buy a high performance if you wanted. Reason I say H.E.I. is because it's the easiest to install and stuff because then you don't have to find a place to mount a coil.
I think I covered just about everything you needed to know other than obvious stuff like swapping thermostat housing over and hoses and stuff.
