Back again with another thread regarding my right stuff rear disc conversion. Have been "fighting" with this deal since installation. If anyone has installed this kit on a 12 bolt did you use any shims on the mounting plate? Starting to think I should have but it appeared that they worked sans shims when initially installed. Since the pads have literally burned down now it looks like I may need shims...just about ready to scrap them and go back with the drums on back...

I installed one of these kits on my 12 bolt I just built. Mine's probably different than yours because I'm running Moser axles which apparently have a thicker wheel flange than the stock axles have. I actually had to take my caliper brackets to a machine shop to have .250 inch milled off the mounting flange so the calipers would be centered on the rotors. Make sure you're putting your caliper brackets on the inside of the mounting flange not the outside like the drum brake backing plate was located.
I actually called right stuff detailing before I milled the brackets and told them the calipers would not line up and they said their kit was designed for stock axles only.
I doubt this helped you but hopefully it did!!

Yes, different rear end setups will need different solutions.

My Strange S60 rear needed a washer added to the caliper mounting flange to move the rear calipers inside toward the center of the car.

The calipers must be centered on the rotors to get good brake pad life.