Don't know about GMC's, but the Newport unit I put in my '47 Chev. a few years ago came with very detailed mounting instructions, which were very accurate. I guess I'd see if you could get a copy of the instruction sheet from the company.


Rich
1947 Loadmaster
1947 Chev. Loadmaster
1959 Chev. Viking 40

Life is short--eat dessert first!