Are the front bucket seat backs interchangeable from driver to pass side on a '72 Supreme?

 

Yes. All of the 66-72 bucket seat backs use the same springs and hinges on both sides. Obviously the 67-68 seatbacks have the RH/LH release buttons, but you could still physically swap sides. Some cars have different hinges to allow the seatback to angle towards the center of the car when you fold it forward, but the 66-72 buckets do not.

 

Thanks Joe, does that also apply to the plastic on the back of the seat uprights too?

 

Yes, obviously allowing for where the seatback release is located on the 67-68 seats.