Get some new bushings. Make sure the frame is not rotted where they sit. Line the frame up properly with all the new bushings in place before you tighten any bolts.
Do a search on body bushings and/or frame bushings. There are already some pretty good directions around from a while back, but if you need more, we'll be here.
On dimension J, either it was measured a little sloppy (straight across 2 plumb bobs on a crooked car?), or it was hit in the rear or elsewhere once, or it is 35yrs old and has succumbed to the effects of gravity and/or torque... or maybe some other reason. I wouldn't worry too much about unless it causes a problem.
I agree F being short could cause the front left wheel to be sitting back too far, and could easily be because of the bushings.
