I spoke to Carey about the Porsche Boxster engine/transmission vs the Subaru. He confirmed that the Porsche transmission is a little shorter, but that he will still need to move the firewall a little forward at the bottom. He said the rear 2 x 2 frame rail will get angled inward at the bottom, but that the top will remain in the stock location. They will adjust the motor mounts as well. He said the seat location will remain the same as well as everything else. He also said that they can adjust the wheelbase plus or minus 30 mm and that since they make their own axels they can adjust everything if it needs any adjusting and can also use different CV joints, including 930 type high angle ones. But that it will not be necessary for my car.