My 91RS originally had a 10bolt open rear end, 3.23 gears, drum brakes. I have swapped in a 9bolt posi, 3.27 gears, disc brakes. This is a Borg Warner unit out of a 87 Iroc.

No problem with swap, and car stops great. My problem is with parking brake and adjustment of the disc brakes. From what I can determine, for the unit I have installed, there needs to be an adjustment rod at the "equalizer" to adjust the parking brake cables. There is not an adjustment located there on the 91 model.

I think I need to find an adjustable "equalizer" from an earlier model to help in solving this issue?

 

Solved my issue. Removed center console and found spring laying on floorboard. This spring is supposed to be attached to lever which when parking brake is applied rotates a cam, applying tension to the cables and adjusting parking brake. Reinstalled spring.

Parking brake operates as designed, brake pedal is no longer spongy, car stops straight and much shorter than with original drum set-up!

Have no idea how this spring happened to come off, but lead me down many roads before I solved the problem. Hopefully this experience will help some one else down the road.