I've got several sets of control arms from past project and parts cars and I'm trying to get them sorted between the A-body and B-body arms.

Is there a measurement for these, maybe from the torsion bar center to the ball joint mount?

I tried searching, but came up empty handed. Thanks guys!!

Look for the letters on the front flat side of the LCA's.
Scrape away the dirt and grime, and or surface rust to look for the letters.
RW BJ would be B & E body
VL would be the A body cars.

73-76 A-body

The easiest way to tell them apart is to look at the bottom edge. The A body arms are flat across the bottom, the B body arms are curved. The pivot shafts are "stepped" on B body, the A body pivots are tapered from threads to the bushing.
Finally, the B body arms are actually SHORTER from ball joint to pivot shaft... kinda wierd.