WHOA!!! What happened here ?
All E-body seats fit all E-bodies. You need the E-body seat tracks so even though the B-body buckets look similar they ride higher then the Es. (taller seat tracks) Not a good thing because you already have too little room between your knees and the bottom of the steering wheel. The '71 to '74 B seats do bolt right in though and you can level them with some washers
As with everything else you had more options with seats in '70 and '71. Different patterns, Leather was available and most had the hard Seatbacks with the tilt buttons on the side. The later models seats were plain looking with the soft seatbacks and tilt lever on the back