Sorry to bring up an old post. Don't know if this will help. I have a supposed 336 out of a '58 GMC 2ton. There is a 336 by itself, no other #'s, stamped on a pad above the oil pan near the dipstick. Near the front of the block (think piston #2) is what looks like (cast) 533087. The pass head has 528511 on it. The engine has a 2brl carb with an adapter for small bolt pattern to big bolt pattern on the intake. Even has the spin on oil filter on bottom pass side.
This engine was definitely in a big truck. Huge frame, huge radiator, & huge generator. I still have the frame from cab forward & 4spd that used to have pto & drum parking brake.
