I think I did read and understand the question. In a nutshell you were asking what offset you would need on the GM wheels to keep the Ford fenders from rubbing the tires. Since we have no idea how close they are, how can we give you an appropriate answer? I think True Value sells tape measures. smile Don't take it so personal.

1953 Chevrolet 3600
Fried Green T'mater (Vern)
In the Stovebolt Gallery
Caution: Political Statement
Man who runs in front of car gets tired, man who runs behind car gets exhausted.