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FYI that someone posted a thread on this (like wk057's thread about getting the retrofit, but maybe elsewhere). They included the printout from Tesla's guides about changes to make in the door paneling for this. It will work in older cars, but you have to change one of the mounts a bit in the door panel and reprogram the air bag controller b/c the seat-mounted airbags in the next-gens have a different position than the original seats.
Again, NOT a problem. But just keep in mind it is not simply unscrew and unplug old seats and screw in and replug new seats.