[72cs20]

I wouldn't really call it a problem. It is just addressing one more minor, but important, step in securing the later cross member to these earlier frames. It is really not a big deal.

Back in post #8 I put up some photos showing the upper mounting holes in the cross member L-bracket that are the same for the 62 and 72. Using these holes will locate the later cross member in the right spot. Then you mark and drill or slot for the rest of your mounting holes. Given the height differences between the 60-62 and 63-87 frames, I don't see how you can't have a small gap at the bottom of the frame. It is easily dealt with. Your experience with the 78 piece may be different in some ways also.