You still need to get uprated front and rear diffs. Front first, Thickwalled Casing and an ATB will do for 500bhp. Here is mine





If you are on a budget and are not going to be launching the life out of the car, then just get a standard 4wd rear diff or 2wd rear diff. Will be upto the job

Are you starting completely from scratch or do you have any parts? if its from scratch and you want a genuine and reliable 500bhp then 10k might not be enough for new engine, Turbo, wiring, ancillaries, ECU, intercooler, Diffs, box, etc etc etc...

I'll call Martin and just explain what you want and EXACTLY how much you have to spend... pls call ONLY if you are serious and don't just thinking about doing this though.