1972-93 Truck seat question.

Garrett Ellison said
Click on this link and you'll see the vinyl covers. Vinyl Bench Seat Reupholstery Kits But, yes, they did change the seats from the '72-'78 style to '79-'83 seat.

What changed? I'm asking about the seat itself ( dimensions, controls, hinges, etc), not the style cover.
So far, this is the ONE guy who says he interchanged covers from two different year ranges.If he is not mistaken, looks like it fit just fine.

Thanks for taking the time to answer!