Sorry, forgot to add: if you want to get really expensive, let's junk the whole 280ZX FI manifold, buy a triple carb manifold and a set of three twin throttle bodies (preferably the new roller vane type), couple with suitably sized injectors and programmable ECU, all the head tricks known to Z-kind, a maxed out cam.....then go kick some carburetted butt.
Oh, BYW, do it in a 2 seater 280ZX to minimise the weight disadvantage that you'll be starting with, strip to the bare minimum, uprate to 3.9:1 diff at least (with LSD of course) and try to make those swinging arms on the rear suspension make some semblance of traction.....
Oh, what the hell - stick the whole lot in a lightweight 240Z shell and have done with it.....