Hy Mathew Blair, I believe the serial number plate in your picture came from a 1955 second series GMC 350 series with a 154" wheelbase, originally equipped with a 316 c.i.d. Pontiac V8 engine. Obviously these specifications do not match what you have now, the engine you have did not come out until the mid sixties and the serial number plate is from a single axle truck not a tandem. If you provided pictures of the whole truck we may be able to find some clues as to what components make up what you have there, hope that helps.
