Can you look a little harder at the tires for size? I didn't think GM ever used an 18 except in a dual application. I'm not speaking from certain knowledge, just what I've seen...

I expected to see dually type wheels.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...