I pulled these out for my 1989 Ford E-150. Will put them on Craig's list at some point but decided to start here. They are in good shape and very clean. I changed they out because my wife and I could not get comfortable in them.
The bases have a 3x7-1/2 bolt pattern in a 5x9 base plate that attaches to the floor. The seat base is 9x12-1/2 with at 8x11 bolt pattern.
Seats and bases $150 and are located in Corvallis, Oregon.
"A straight line may be the shortest distance between two points but it is by no means the most interesting". Jon Pertwee as Dr. Who, The Time Warrior.