Maddat over here do a RX7 series 4/5 kit that will bolt in but i'll probably go for r32 4 spots or similar, have to keep it Nissan
As for the rears, a shortened Skyline rear may go in, so just the standard R31 discs from there will stay.. Still have a lot of work to do !!!
Keep us updated on your build as well, always helps to see how other people are doing things.