Your bracket and frame appear to be sound even with the 40-50 years of "hammer fitting" due to looseness.
If it were mine and I was building it for the son which I care about, I would bolt the bracket back in place (rivets aren't necessary for this application).
The only affect that the moved-around-metal may impact would be the cab height adjustment on that corner, which can be completely addressed with a shim at the front cab bolt between the cab and the frame. You need to check that anyway.
Carl
