ATTENTION: If you have oem drums...disregard this. This is for disc cars only.
I have a strange 12 bolt which uses the small gm pattern housing ends but with a 3.150 bearing. It's called a "Strange" Housing End. It's designed to work with stock 93-97 rear brakes which use the same calipers/ guides as the 89-92 PBR's. Also I'm told that 89-92 and 93-97 rotors interchange. The only difference I understand is a very slight rotor diameter difference. The offset is 2.75".
I'm using Baer 2301012 Eradispeed+ 2 pc. Rotors from an 88-96 Vette which only come in 12" diameter.
I had to order Baer backing plates 6710056 & 6720056 which allow for a 2.5" offset along with four .250" spacers and four bolts that are 5mm longer than stock.
Baer says that they now offer a backing plate that allows for 2.75" offset w/o using the spacers.
The inside diameter of the rotor hat requires the wheel flange of the axle to be 5.90" max. diameter. My Strange axles are 6.240" so I have to have the alxe flange turned down on a lathe. No biggie.
Baer first told me this would not work. Especially Bill there. However after a few calls with Rick and Dutch at Baer, I was able to determine that this was possible to do w/o making a set of custom backing plates.
I know several guys have wanted to upgrade their PBR's to the 2pc Eradispeed rotor. You may have to experiment with spacers/shims to get the caliper offset right, but as long as your wheel flange has at least a 2.5" offset from the backing plate flange...you should be fine. If for some reason, your rear had less than 2.5" offset: you'd have to use a different backing plate than these (if they have one).
I know that if you're considering getting a Moser rear...You can get their 12 bolts with the Strange housing end. They'll accomodate whatever width or brake offset you want also. I assume they can do the same with their 9" rears too. Therefore the above info should also apply. Just be sure to ask for a 5.90" wheel flange dia.
Good Luck!
Dwain

 

Good info to know.

Do you have the price on these pieces handy? Just wondering how much more I'll have to put into the car.

 

Tbyrne got me the best prices on a gp. They were still high though.
You can go with one piece rotors also...like EBC and it'll be cheaper. You wouldn't have to upgrade to 12" rears though. The reason I went with the 12" rears is because I wanted the 2pc Eradispeed + rotor and that's the only one they offered.