I've always thought the biggest problem in trying to save money buy putting together your own parts are that
1) brake bias, they vary from car to car, specific brakes are made for specific cars. IE evo calipers wont work on a 335, nor will they work for a honda civic
2) weight, cars weigh differently, therefore is it possible weight can have an impact on how brakes are engineered?
Afterall these are brakes we're talking about, a hack job wont cut it as it can be very dangerous. Although I understand people skimping on fake body mods and wheels, this one I'd be much more apprehensive about...