Been thinking about a trans swap for my '86. It's a 351/C6 with a 9" 3.0 gears. I've gotten spoiled to overdrives I guess, but this thing drives me nuts on the interstate because of the rpms it's turning, and the mileage SUCKS! I know a 351 won't ever get great mileage, but most of my driving is interstate, and usually 75-85 MPH. I rarely tow anything with this truck (that's what my '94 I6/manual trans is for). and rarely haul anything heavy. It's more 'toy' whereas my other is my work truck. Anyway, I want some kind of overdrive, but can't spend a huge amount of money. My first choice would be a ZF 5 speed, and I know I can handle the clutch pedal/master cyl installation OK, but the cost is prohibitive. I'd kinda like a E4OD, but it's a non-computer vehicle and the cost of an aftermarket controller is also too much for me. That pretty much leaves either the AOD or an overdrive 4speed. I was thinking of buying a core AOD and building it myself(I've built one GM automatic, and found it's not as scary as people make it out to be). I'm just worried about durability, and was wondering about mods/upgrades (EAOD parts I've heard about) and any differences between car/truck models. I'm also planning performance mods on the engine in the near future, so I want it to hold up to that as well. Any suggestions or experiences would be welcome.