Small question about disc brake swaps
73~76 A is the same as 70~74 E
the 73+ B and the 80's F/M/J/R is about 3/8" taller and will work fine, and works even better in an application with a lowered car. it's also a lighter casting by about 3lb
you can mount any disc brake kit that is designed for the big ball joint upper, so the years/bodies listed above.
i've installed and sold tons of the FMJR spindles and even run them on my cars and never had a problem with alignment, steering/ride or bumpsteer.