Yes, the Hydra-Matic in the '50s Chevies and GMCs was a 4 speed. First offered in '53 on GMC (first automatic in a truck) and '54 on Chevrolet. GMC was the first to offer an auto with 4 wheel drive, in '56. Chevrolet didn't offer an automatic trans w/4 wd until '68. Also, the V8 option w/4wd wasn't offered on a Chevy until '60. Some other differences, GMC offerd 4x4 on all models, including the long 1/2 ton, Chevy didn't until '61. GMC also offerd a factory/dealer installed Chelsea PTO w/Spicer drivetrain and a 5 ton Breaden winch, Chevrolet didn't have that, either. GMC offered that option up to at least '70.
