I have a collection of seats here. The older (up to the 22 change) Model S and X seats are quite a bit more robust and larger than the Model 3. They are wider, thicker, and longer in the base. I can't speak for the upper but presume the same applies.
But the newer Model X I have is 20" wide on the base, while the Model 3 / Y is actually a bit wider at 20 1/2" when I measured both.
So if you stayed with the newer 2022 and later Model X (and probably S), the seat bottom might just fit.
What are your objectives in changing the seat out?
The older Model S / X seats 2017-2021, had a wire loop OUTSIDE the metal seat base. Although all models used the same seat base, that wire loop make the seat support much wider and the wings and bolsters much more sturdy. Those wire loops make the seat base impossible to fit into a Model 3 / Y, I believe.
The newer Model S / X seats 2022-2023, had the wire loop INSIDE the foam! Making the foam base NOT wider than the Model 3. The 22-23 Model S is your best chance. The seat is overall smaller than the older Model S seat.
There's also electrical compatibility issues. Although the seat weight sensor on the driver's side became the same in 22, the seat heater wiring is not compatible, and I'm not sure why. They may have additional sensor capabilities in addition to a different seat heater system.
I don't have the upper seat, so I can't measure.
An additional challenge is this. I've seen many people complain about the newer Tesla seats. The Model X (and presumably S) from 2022 up, have a metal support structure within the foam. If you are a larger framed person, that metal might start to hurt you like it does so many of us. The larger bolsters at first seem attractive, but for many come at a cost.
What are your objectives in changing the seat out?
