Re-building and getting ready to install the rear, I have double adjustable upper control arms with johnny joints on one end, can I use the poly bushings in the ears or will those bind?

I'm wondering this too. I want to say this would be the most precise setup.

Some say the rubber bushings allow a little flex and it helps, I went with poly from UMI. I have had no trouble with that set up.So far with no front suspension work, the car 60' is 1.5x . Thats not great , but dont think it has anything to do with bushings.

with a standard (OEM) four-link you can use poly bushings top and bottom without binding.

it is the WATTS linkage setup that can't use upper (control arm) poly bushings without binding (IE 1st gen Rx-7, Crown Vic)

What is the length of a factory 12 bolt rear housing for a 72 chevelle?

http://carnut.com/specs/frear.html

TRZ has a neat Heim like bushing that looks like it would work good. http://www.trzmotorsports.com/317.html#rear