I just picked up a Bench for my 69 RR (to replace the buckets in there now), and I dont think they would be interchangeable. Its out of a 69 Satellite.

If you need a specific dimension let me know as the seat is sitting in my garage. Also as far as tracks, my references quote "Seat Track rails were unique for each model year and seat type and the correct rail set must be used with the coresponding seat". "The rails were unique to the B-body line. Other track rails from other car lines wont interchange." "But not all bench seat rails will interchagne even though they are from a B-body and are the correct model year. Those from a four-door or station wagon wont work because the seatback is solid and bench seats in the coupes have a split back seat rest."

Hope this helps...