for the seat bases, I know that the passenger seat base changed at some point for the FMJ cars. I had to use the older base from my Volare's factory passenger front seat as the hump for the catalytic converter changed from the 5th Ave I got the interior from.
The FMJ cars used a bench seat, a bench with fold down center armrest, the 40/40 buckets, and the 60/40 combo. The seat shapes stayed pretty much the same except for the highback buckets. The covers should then be pretty interchangeable.
For other Chryslers, the Valiants had seats that were not similar. The B body cars, like the Satellites and 75-79 Cordoba had differently shaped seats as well, even the buckets were different, of an older style. The seatbacks of the bench seat with fold down armrest as was standard in the 75-79 Cordoba were of a similar shape to the 60/40 seatbacks but I don't know if they are the same. They did not recline as I recall.
The big C body Chryslers usually had the 50/50 front seat tho the later 70s B body, the R body cars started to use the FMJ 60/40 seats. They're even more rare than 5th Aves.
So, the FMJ variants are pretty much the ones that are going to slip on as if they were meant to.