I just went out to the auto recyclers and bought a pair of seats out of a 2005 chevy pickup. They have seat belts incorporated in them, the bottoms bolt to a relatively flat surface, lumbar adjustment, and they also fold forward so I can get behind the seats. I plan on installing them in either my '65 IRWIPI truck or a 1960 pickup I have. You can also get the center console/seat section, but I elected not to. I'm not sure of the total width with the center 20% section. I bought the manual version in a velour covering instead of leather. The leather seats were quite expensive.
2 door Cadillac seats will also flip forward. Some of those may not have the seat belts incorporated in them, bu tthey sure are comfortable. I am unsure about the mounts and how flat they are. If you get electric seats, remember to request the pigtails for the electrical.
