Splines (GM tended to use finer splines discs), gears (each mfg of course specs their own gear sets to match their engine) and lengths (a lot of variance in tailshaft lengths, but luckily most interchange).
T-10's were used in everything. AMC's used them and so did Studebaker from 61-64. The mounting flange to be mounted to the bell housing were usually either Ford or Chevy. This was the big diiference between input shaft length, splines and mounting.
There is two (well More than that) different GM T-10's, the later ones 75-76? up were calles super t-10'. The early ones both had ten spline inputs, but ford used 1 1/8 spline I believe, Both had different out put shafts, shifter locations, bolt housing patterns, etc. The really old ones weren't very strong.
The Jalopy Journal
