Starting in 1955.2, if a v8 was desired in the GMC, a Pontiac was used. I believe I read if it was going to Canada, then a Chevy v8 was used - but in the U.S., a Pontiac. In 1955, it was the 288 (even though Pontiac called it a 287). In 1956, it was the 317 (Pontiac was a 316). In 1957 it was the 336 - I think a destroked Pontiac 347. I'll have to check that fact.
