'84 rx7...
first generation?
Well, first up, you've already got a potent car. Yes, rotary and all. Be careful with the engine, you don't want the darn thing to break on you. You're likely to swap engines before trying to repair it. You could look around for some rare engines, like the 3 rotor motor (500Hp is quite easy with the 3's) and then find a mechanic who's willing to undertake the daunting task of trying to fit it in that shallow engine bay.
If it was me, I'd just upgrade the blower to a slightly larger one, remove iar conditioning, heater, any electrical components that might be heavy.
I'ts really a quick car, just that technology has overtaken it. Transmission leaves much to be desired, but it was ultimately the tires that blew, not mechanics, that threw victory away for a racing friend.
I don't think it needs as much precision as the 3rd gen RX7 to exract max potential out of it.