While it seems everyone wants to sell you the GM "metric" calipers for "their" conversions, the various Ford/Lincoln rear disc brake setups from over the years have calipers that are probably just as common, with the 38MM Varga rear caliper from 94 and newer Mustangs the most common and easiest to get. It also has the parking brake built in and would require only cable adaptation to get a working parking brake.
In the spring, after the weather breaks, I'm figuring to use 54MM single piston with parking brake calipers from a Mark VII on my stock axle ("B" body, LBP to Duster), stock roller bearing, 8 3/4 along with the matching 11 1/4" diameter Lincoln rear rotors (rotor's center pilot hole will be matched to the axles).
The 73MM front calipers these rear discs came matched with from the factory are very close in size to the 2 3/4" (69.85MM) Mopar ones and should balance out nicely with an adjustable proportioning valve because the slightly smaller Mopar caliper is going on the 11 3/4" diameter "cop car" rotors (up from the just under 11" Lincoln ones).
Making up "C" shaped caliper brackets out of 3/8" plate to mount on the inboard side of the axle housing flange with longer bolts would allow use of the stock bearing retainers.
A master cylinder with a 15/16" or 1" diameter piston should be about right for manual brakes (I think the one the Duster has now is the right diameter, but it might not have enough reservoir capacity to accommodate rear discs), and a Mustang 1 1/6" disc brake master could be adapted to the "A" body bracket, booster, and linkage for a power setup.
I'll do a step be step photo essay and share when the time comes.
