When you say 15" rims, do you mean stock rims? If so, you are not going to be able to fit a 4 piston caliper. Those calipers require an amount of backspacing and offset that the stock wheels simply do not have. You can probably fit a 2 piston cobra/ pbr caliper, but you are gonna have to fabricate a mounting braket and/or modify the spindle.
By the way, It;s good to have another Bronx member in here!