Being a 5 speed out of a 49 GMC, it would almost have to be a Clark transmission. Either Direct Drive, or Overdrive. If the truck is still around, it would tell you on the plate that was on the back side of the glove box lid. 5 speed transmissions were standard equipment in the 450, & 470 series trucks. My 52 model 470 series, has a Clark 205V 5 speed in it. For 1952 there were model 204VO, 205V, 207V, & 207VO transmissions available.
