528e is not a good racer. the cam is cast not forged and cannot handle the RPM's. cheaper to find a 535. but if you really want to...
you will need 325i heads, cam (or 524td cam ) and throttle body, mm I forget which pistons 535i?
you can actuall pump 220+hp, about wut a stock 535 does lol. but a good start would be a 325i diff, as deep as 3.54 and LSD even mo betta

just enjoy the car