Well, Martin did ask for casting #'s.......
The displacement is stamped on the machined boss to the left of the distributor and will start like "A248******" In this case the displacement is 248.
Also, on the door post should be the model # and serial #. Something like "354-24.....". The "24" would be to designate the truck came (in this example) with a "248". Martin, yours is probably a 228, but casting numbers will tell all.
This is how my '51 was, I'm not sure about earlier models. Check OldCarKook\'s site for more info.
Martin, Welcome to the 'Bolt! grin cool


*** GMC ***