What are the true weak points of the 5HP24, if you exclude the scored pressurevalve which cause pressurespikes that break the A clutch drum, and the failed C drum bearing which cause the A drum Oring to fail.

Lets say you put a 500hp 4.2 in front of this gearbox, what part of the gearbox is likely to fail?
(Except for the fact that you have to deal with extra cooling of the oil)

 

I can't realistically answer your question, but I can tell you that if you do that, you will need the largest externally mounted transmission oil cooler you can fit in front of the condensor.