Mid-1950's GMC's had Pontiac overhead valve V8's as an option, usually with the 4 speed Hydramatic transmission. I drove one tractor-trailer rig with that combination, so it was not just limited to pickups. Way back in the 1930's I believe some GMC's ran Oldsmobile flathead 6's.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!