They made lots of different valve body combos--we always use Turbo Action Cheetah on Mopars--TransAct used to have a better trans brake in the way back days but now the COPE, A&A ( same) are the better transbrake--for straight up manual the TA is by far the way to go--Try CRT--Cope racing Transmissions in Indy--he is straight up and buys all his parts from neighbor and 727 legend Rick Allison at A&A He can set you straight and is trusted source here for all Mopar needs I raced a 904 for about 10 years we used low gear set from smog era unit and always use the wide front band and drum--front band adjustment or rather keeping after it is the KEY to 904 success period! Always check converter when out they usually crack the hub at drive lugs--never worried about it in door car fix at end of year but in dragster eehhhh....We adjusted front band after two-three runs then checked it every few wk ends--
TransAct has crappy rep here in USA--
I bet you have a pro type that requires the button to reverse--try it