The bolt pattern on the front of the trans. is GM, or Ford, or IHC, or Dodge, etc. They come w/ large, long input shafts(not very useful), and short input shafts. Parts are getting hard to find. An excellent, close ratio trans, OD ones are rare. I mated one to a Dana 20 in an early Bronco, and Dana 241. Look in 1.5 ton trucks, never came in pickups. Most yards don't know what they are, don't bother asking, just look. Al top cover w/ 4 shift rails, two steel pins in top of Al housing shift ball rotates on get loose, wear item.

'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.