I think I read on the TTI header site that A body engines are offset to the pass side 5/8 for 63-66's and 1 1/4 for 67-76's. I found the reference when I thought mine was wrong.
Sorry this has nothing to do with it. Look at old Jeep transfer case to rear or front axle sometime. They are angled horizontally. "Why it works" is that the shafts are PARALLEL which is what makes U joints work "proper."
My old 62 FJ-40 had a centered rear pumpkin and offset transfer case. There was a huge horizontal offset between the two.
