Title says 54 Chevy Motor No. H54T####.
Is this same number on the serial number plate inside the driver's side door? It looks to me like a Chevy serial number, and if it is the '54' means 1954.
On the other hand with a GMC motor and GMC front sheet metal you're not going to be safe betting a serial number will correctly identify all the right parts.
And that is the wrong rear fenders for that truck, and I suspect the bed came with the fenders and is also the wrong bed, though I can't confirm that from the pictures.
