CRX si would be ITB, not ITC. Does it have a carb or is it fuel injected? It might be an ITC car with a carb but with si bumpers and bodywork. (which isn't legal for ITC, but bring it to GLD and we wouldn't care).
There are no corresponding solo classes in SP for ITX or ITE, so if it isn't a legal ITB/ITC car, you can't run SP (not legally anyway).
If it is a legal ITB or ITC car then you can go to the matching SP class, which I think changed recently, so you'll have to look up the matching SP class, but ITC is limited to 6" wheels and ITB to 7", right?
But you already know that it's not just wheels, you have to make everything IT legal to run SP.

On the third hand, nationally you aren't going to be remotely competitive in SP, but you don't have to win for people to be unhappy if you aren't legal. If you finish 20th out of 24, there will be 4 people not too happy, depending on what isn't legal on your car.