I wonder why GMC cabs got these and Chevy did not.
GMC's were built stronger for the "professional", where the more affordable Chevrolet's were built cheaper for the homeowner/small business types.
The big GMC trucks from 1955-59 (and maybe other years) also had door wedges to keep the doors from opening when the cab twisted. They also used a three piece big back window where Chevrolet used one piece for their Big Back Window, this also helped make the cab stronger.+
Mike B
