i had a national 4x4 four parts chain store re gear my diffs. took it back a couple of times, once it got towed back on there dime. They never got it right, i ended up just buying complete axles of cl. lesson learned.
sounds like the starter solenoid to me, i had the same problem. i modified my solenoid and added a ford solenoid to the firewall, starts every time now.
i was using belts from oriellys, and could never keep my belt tight, change it one from nappa, it was way wider and thicker belt and solved my problem.
i got tired of messing with my column and rewired a switch in the dash, like the 67-72 chevy trucks had. i also bypassed my neutral safety switch. i like simple.
i installed hid in my 75, it was plug and play, the headlight housing does make a difference. On my old toyota truck i have hella housing, they throw a better light pattern than the cheap knock offs on ebay.
the good kits are plug and play. the cheap ones just plug into the harnes, the ddm tuning use a relay and get wired to the battery. which works the best.
http://www.fixmyrust.com/index.php?app=ecom&ns=catshow&ref=73-87_Chevy_Pickup_Floors&sid=1sk864fp385q6n0omdc1p8y8rvc24a07
buy some parts and replace what you need, i get my patch panels off of ebay