I added another picture on original thread showing how protruded the backing plate is and I think I could cut a sliver out of in and hammer it in flush, a little weld and drill new holes in
Yes, you could certainly do that. You'd need to know how far back of center the cable attaching holes are in the '51 backing plates to get the cable in the right place. The hole for the cable is also irregularly shaped (kind of triangular, IIRC.) I can't measure for you as my chassis is covered in snow (and getting deeper currently.) Here's the best picture I have of that area.