I am going to take a guess at this one. The later panels shared the same fenders between GMC and Chevrolet. The 1948/53 Chevrolet and GMC rear fenders are the same, the front fenders are identical except for the parking lights on the GMC. I would say that the earlier panels, GMC and Chevrolet used the same fenders too.
The changes in the bodies were subtle, mostly in the grilles and hood and different emblems and ornaments.
