70 thru 74 bucket seats

As Alaskan T/A said the frames can be interchanged, there are year to year differences so if you're looking to keep the original appearance then you have to keep the year ranges right. If you're not worried about looking totally original it doesn't matter much. Some yahoo put 73+ buckets in my '71 Sebring plus. They fit just fine, just like the originals, but obviously the upholstery style is wrong, the seat backs aren't separate pieces etc. Someone also recovered a set of '70 challenger bucket seat frames for my '72 challenger, I figured that out because they left the build sheet from the '70 and dyed the seat backs. Even recovered they still got the pattern, but they fit and function just fine.

But the seat tracks can't be interchanged between the body styles, you need A body seat tracks for an A body. And don't buy a set of tracks for a '76 A body to use on anything earlier, the inside tracks are different because the floor was different to clear the catalytic converter.