If I didn't modify the firewall, I'd prefer the wagon belts. They're a cleaner installation I think. In my setup, the sedan belts were my only option. The belt slot in the aluminum seems awkward. I added a little bend to the slot area to help it feed better.

Doug , if you get a set of sedan belts in the mail, the spools will be locked. Loosely bolt them into position and give them a strong pull, then release. That should unlock the seat belt spool. It's what I had to do. TK, in Akron, has a box of belts if you come up empty. Somehow I had one extra, but it is damaged with missing parts.