Hmmmm.....
Just another thought.
If you do use hemi joints then not only will you be able to adjust the fore/aft/in/out position of the outer point, you will also be able to move the joint itself forwards or backwards due to being much narrower than the 1.3/4+ width of the regular fittings.
You could re work the lower rear control arm to position the upright in a more suitable position.
Looking at the picture with the body on it looks like the body would fit better if it were moved forward to line up with the dash mounts and door hinge mounts.
This could just leave the front end suspension in need of "adjusting", as clamping everything to stop it moving during welding will require a substantial fixture.
Anyway. Just some thoughts
I'm not trying to say that you should bodge (English term) it all but might be less drastic than stripping the chassis back to the main rails.