Is there a data plate on the firewall from Chevrolet? Is there a Service Parts Identification plate somewhere on the bus (normally on the glove box door)? Lets see them...
Have you pulled the drums?
Measure the drum inside diameter and shoe width (example 15 x 4).
Do you know they are out of spec and can't be turned? Any big truck service shop should be able to turn them for you and reline your shoes.
Mike B
