Thank you for the clarification, this is helpful to me and those that don't know the details of swapping used parts on their projects.
Sure, glad to help. I received plenty of input from nice folks here and elsewhere, so happy to give back.
By the way, I did a separate writeup about it, but the reason I'm familiar with the seats is because I wanted to install a Thunderbird power seat base into my 66 Galaxie. Some people said it wouldn't work because the floorboards are different. Others said I'd have to do a lot of welding.
Turns out the floorboards are indeed different, but only one way: the T-birds have shorter floorboard pedestals front to back whereas the Galaxies are deeper. Hence, the bolt pattern on the T-bird seat base front to back is shorter.
However, the bolt pattern width (side to side) is the same on both T-bird and Galaxie seat bases.
The easiest thing to do is simply drill new holes into the floorboard, then mount the seat base. But with the restoration I was doing, I didn't want to alter my floorboards. Instead, I fabricated adapters using U-shaped flat bars.
It was easy. I just drilled two sets of holes - one to match my floorboards, and the other to match the studs on the seat base. Then I used high-grade bolts to anchor the flat bars down. That's key given the g-forces at stake under hard braking.
End result is that now I have the T-bird seat base under my original seats using the adapter bars on the floorboards. But to the eye, everything looks 100% stock and original.
A few other notes ... first, Ford only offered 4-way power bucket seats in 1964-65 Galaxies and T-birds. In 1966, Ford came out with 6-way seats. The same switches, motors and relays were used on both Galaxie & T-bird bucket seats. Galaxies only had a driver's seat available, whereas T-birds had both driver & passenger.
In 1967, Ford changed to a different type of 6-way seat and switch. Hence, the 1966 version is a one-off.
Add to that, power seats was a $95 option back in 1966. Adjusted for inflation, that's $728 in today's terms. Back then, stuff like power seats, windows, etc were luxury items that fewer people could justify. Point is, the percentage of buyers who opted was very low.
Today, finding a 6-way LH power bucket seat from a 1966 Galaxie is pretty rare. Conversely, there are many more available from T-birds in part because those were more "luxury"-based cars and dealers added pre-optioned cars to stock their lots. So it's a ton easier to find a 6-way power bucket seat (or seat base) from a T-bird than it is a Galaxie.
That's what led to the question about mixing & matching.
However, it's worth noting 6-way passenger bucket seats are somewhat rare on T-birds. It was another cost-adder on top of the power driver's seat. Hence, the RH switches are highly sought after because of the seat rarity and the fact they're a one-off.
Lastly, interestingly enough the "recliner" seat option is a similar story. Few Galaxie buyers opted for it and it's not very common to find cars with a RH reclining bucket seat. But they were much more common on the T-birds. Moreover, Ford realized they needed to move out all remaining `66 inventory to prep for the new `67 models with different seats, so they started adding recliners as a no-cost feature.
The RH bucket seat recliners are the same for 1964-66 Galaxies and T-birds. But the actuator inside isn't reproduced. It also adds another 25lbs to your car. Still, a pretty cool option for back in the day.