I looked in to the rules and classification a bit and didn't find a specific class for your car aside from S4. With that being said, if they clump all 4WD cars together and you have to keep the stock block for your specific car (unlike the update/backdate rule in solo 2 for NOC Imprezas) then I think you're SOL.
To get clarification on the internals I suggest searching over at RS25. I don't have the answers for you, sorry.
I'm going to shoot you a PM about CRS
