Hy Straightjacket, in 1939 GMC introduced a new series of engines with full precision bearings (no babbit), these engines were the following cubic inch displacements 228, 236, 248, 256, 270 and 302, this series of engine was used up to 1959. Only the 270 and 302 were in use at the end of the production run. I believe the engines were painted a unique red colour. There have been books written in the fifties on hot rod mods to these engines and Chevy sixes of the time, hope that helps.