GM metric calipers from AFCO are designed to be used as a new stock replacement caliper.
Calipers feature a stock appearing caliper body, new ground 2.25", 2.50", or 2.75" stainless steel piston, and low drag seals
These calipers allow for great brake torque bias tuning.    *2.50" bore is required for IMCA applications
 
Note: Requires a 10mm x 1.50 Caliper Fitting