Richard D. You covered the subject well. But we are talking about two completely different lower floor structures. I have a 73 that I'm fixing up to sell. And I'm finding the differences to the later GMC's. And I've owned, dismantled, and built three 78 Royales. And the 78's. I know every square inch of them. The 77, and 78 were built much stronger in the floor, In the rocker area along the lower outer edge. Hugh difference. I think the floor/rocker strengthening started in 75? Others can confirm that, if I'm in error. There were 3 different GMC groups built. 73-74 then 75-76, and the final 77-78's. Then the 78's built after December of 77. These got the final changes. I don't think the 73 body pads move. I believe the small pads came in for 75? Bob Dunahugh 78 Royale And my lonely 73.
