E36's were extremely "competitive" in ITS, thus the restrictor. And, I suggest they're the car to beat in ITR right now, at least until/unless someone does full-up development on other options. Plus, it's all been figured out, so for you it's a plug-n-play (or, well, buy-and-install...)

But, given that the only build difference between the classes is the restrictor and a little weight, run both classes and decide for yourself...