Wilwood seem to be more bias towards motorbike calipers. prom the comparisons i have made between them when looking for my calipers i found that the piston size was less that the standard R33 calipers and were almost too light. i personally woud stick to the stock 33 calipers. i even found that there was no real advantage on running the 33 GTR Brembos instead of mine. they are the same sized piston in the rear and the fronts are only slightly bigger, both front and rear brembo's allow a thicker rotor to be used. don't forget that you will also want to work out how much pads are going to cost and also rotors. these are usually not cheap. i found that that every 4 sets of pads i would need a new set of rotors. and at $300 a pair of pads and $1500 for a set of Harrop rotors it's not a cheap excersize. just my 2 cents. im sure ppl will probably have other opinions, but that's mine!!