1976 model year GMH assembled C20 truck. 292 6cyl. See if you can find the other plates, the ADR plate will have the PSN as the chassis number (J545961) plus it will have Chevrolet C Chassis on it, the body plate will have Chev C Cab on it and be painted and there will be another black plate with a round top.

If you don't want them i'll have them, I've been collecting these lately to decipher some of the numbers for an article for Mark Oastler.