If you are serious about 500hp, then I'd look at something other than AE86 struts. RA40 and XT130 have bigger stub axles and are easy to swap in, plus give a range of brake options.
Popular brake options are:
- RX7 4spot on custom adaptors. Usually 280-300mm rotors.
- Hilux calipers on XT130 struts and some form of Peugeot rotor.
- MX62 calipers on XT130 struts and RA60 hubs and rotors.
- Maybe Hoppers Stoppers do something bolt on.
Plus any number of other custom setups.
But I'm keen to see your motor.