Originally Posted By polyspheric
The TH400 + GV cannot have a locking torque converter, 4L80E can (but $$$ if you need WOT locked).
Both require D/S mods; shorter makes the angle worse but the D/S will be stronger.
4L80E may need tunnel bashing due to large diameter far back?
Both require serious aftermarket parts for your power level.
GV adds more length, make a worse D/S angle.
4L80E controls are more expensive but useful.
4L80E has slightly taller O/D at .75:1, GV is .78:1, otherwise the ratios match.
GV is far more expensive (than the extra cost of 4L80E over TH400).
See my table of O/D transmissions here:
http://victorylibrary.com/mopar/aod.htm

Did you know there is a 6L80E...?


Just to throw in my 2 cents, the torque converter availability for the 4L80 is not as good as a 400 but with the right manufacture they are out there. The 6L80E is a valve body modification to the 4L80E and some preliminary reviews I read seem to be a little less than impressed. Tunnel modifications to a Mopar to make them both work may be very extensive. Depending on power level I would seek out a highly modified TH200R4 and know there is a vendor that makes an adapter. Converter choices are good as well.
Edit, just reread the OP and see the power goal is 1000HP and may be a stretch for a modified TH200R4.
AG.

Last edited by turbobitt; 06/15/16 09:41 AM.
1970 Challenger w/572 Hemi street car and my pride and joy. 1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno. 1976 Cee Bee Avenger Jet Boat - 460 Ford powered.