The RX-7 and the 135i sound like your best options, I guess.
Personally, I'd probably try the 135i, seeing that its NA and should provide you with a broader power band across the whle RPM range.
m3 csl or rx-7 but you won't be able to drop all the weight off the rx-7. they come in at 1050ish with all weight reduction mods. the csl is a very quick and capable car.
At GBRC We run a specific car class called Class A, 1150kg and max 404 bhp, no race cars. It seems that the lotus Evroa at the moment is the most competative we have come accross, and very strong out of the box.