Very good comments and she's mostly right about the difference between the Gen2 and Gen3 front seats. It's not just the better backrest on the Gen3, they ditched the micro-mini seat bottom for something that belongs in a $23k - $32k car.

I wonder if the genIII seats would bolt into a GenII???

I've not taken a tape measure to it, but I say absolutely not.

The seat rails and mounting feet look totally different than the Gen2. And i can tell you the Gen3 'hardware' (rails and feet) look quite a bit beefier.

I'll betcha no 2 cars in Toyota's lineup have interchageable seat mounts. Toyota really does not want people swapping one model seat into another car. Major safety issues. Don't know for sure, but I'll bet a Corolla seat does not bolt into a Corolla Matrix car of same year.

And it's not just the mounts, there are electrical connectors for seat belt sensor, seat position sensor and airbag. Those vary from car to car.

The seatbelt is bolted into the frame of the seat. One's safety depends on the seat being securely mounted in a car. If a seat mount gives out in a crash, seat and occupant go with it.