I believe you can do the 99+ GT calipers and stock size rotors under a 16 inch wheel. They're also a two piston caliper like the Cobra's and will greatly improve braking over the stock single piston caliper.
I run the '02 PBRs on the stock rotor, but I'm going to go to the Cobra '13s as soon as I scare up some rotors (or have the 13s turned) some coarse threaded banjo bolts and some braided hoses.
Sooooo---once it's done, I'll have some red PBR calipers w/Hawk pads, some fine thread banjo bolts & some braided metal brake lines that'll be surplus to my needs but may fit yours.