Most Porsche wheels are interchangeable. I've used my Boxster wheels on the 928 to test for flat spots on my tires and they fit perfectly. I believe the stud distance is the same on all P-cars (except maybe the Cayenne, but no knowledge there).
The biggest thing you need to look for is the distance from the inside edge of the wheel where it meets the hub and the inside and outside of the rim. You don't want it to be too deep inside (hitting inside the wheel well) or too wide outside (hitting the outside edge of the wheel well). Just compare your wheel to the one you want to get. You also don't want the outside to be too shallow hitting the brake caliper.
Good luck in your search!
