Hmmmn. If two pistons are the goal,seems application of any aftermarket rear street caliper would work...they run a heck of a lot cheaper too...AP,Brembo,Harris,Performance machine...it would be fun to try an old Lockheed even...sorry the tinker brain just took over. I seem to remember Harris making a mini caliper...of course these would not be a straight bolt on...of course I haven't tried any...mebbe I should have another beer.