I think RuffStuff Specialties makes brackets that allow you to use the factory front Tacoma rotors and calipers on the rear, I think they are about $50. Never tried them, but that's the route I'd go. I have used plenty of RuffStuff products, just haven't tried the Tacoma rear caliper brackets.
While you are at it, I would ditch the load proportioning valve (brake bias) under the bed and put a manual one (turn knob to adjust) either in the cab, or under the hood. You will possibly need to upgrade the master cylinder, but that is an easy swap to an old 1" bore chevy master cylinder. I think Sky-manufacturing.com makes the adapter. The master cylinders are CHEAP too, and readily available at any auto parts store normally.
FWIW, the chevy caliper swap is plenty for the rear, those calipers are cheap and easy to find, unless you use the monte carlo ones with the E-brake.