Other pricey/hard to find coupe specific stuff: the rear window is supposed to be in excess of $1000, coupe seat frames are technically unavailable, but can be sourced from Germany for $400 if you substitute a Japanese or Euro part number.

There's an added vacuum element to lock/unlock the seat backs with the doors. I consider it an important safety feature that it work properly, otherwise the seats will fold on you in an accident. Mine didn't work initially due to leak in the defroster vent, but it would work with the ACC set to defrost. You might want to check that.

Otherwise it's mostly standard 123 tech.