did any A body come from the factory with a 904 and an 8 3/4? i don't think so, so any factory driveshaft fitting is just luck. also, U joint sizes matters. there' s a little room for variation in length but not much
904 is same length as an A-body A833 4 speed trans, so yes 904 with 8-3/4 is same as A833 & 8-3/4. The driveshaft in my duster with a 904 and 8-3/4 is 49.27" C-C length
