oops my computer sucks, well below the max input torque and hp, just remember the killer for a 643 is heat keep thethans under 200 and change the filters ad oil regularly and it will last you a while. the 643 may be a pain to get in there, its almost as big as a 4-71 but its doable, I have put a 643 and a 545 in a pickup before the 643 was behind an 8.3 Cummins 250 that was cool, the 545 was behind a 5.9 and after I put on a turbo 150hp injectors and a few other odds and ends we killed the 545. I dont know if the trans comes with an external filter base and lines, if not get one it needs it , they have an internal filter in the pan but the external spin on helps a lot, you can change it when you change the engine oil and it extends the life quite a bit compared to the internal filter alone, and get a BIG cooler they use #8 JIC cooler lines as I recall I cant remmber could be a #6 but they are not your average 3/8" little clamp on line they have too much flow and pressure for that to last. Good luck keep us posted.