You'd need the harness and GTP ECU for sure. Think one of the axles is a different length on the GTP as well, could be wrong. On whether or not its a good idea to swap, well, that's up to you. If you like the S'C then I say swap. If the GT is doing well right now then I'd just leave it be. Or you could just pull the engine/trans from the GTP whole and save it for a later date if the GT develops an issue.