I have a 997 C2 and have a really great deal on coilovers for a C4 and was wondering if they would fit.

I had a similar situation with my last car, a bmw 135i, where I put coilovers from a 335i on it. The difference was spring rate and a bit different valving. I had zero issues with it.

Does anybody know what the differences between the two are?

 

I know that Bilstein has different part numbers for them, but don't know the specific differences. I'm sure the heavier front end in a C4 would require different characteristics, and the mounting may be different on the fronts.