All i know of is Metropolitan and Centurion's And there are a few that i know of that were home brewed. Jeff,Eric,Audra,Kevin,Bob or Malo on here might have way better info on it. Im sure one of them will post in here shortly.
There was also Magnums. I've hear that Metro's were built better than Centurions, but i have yet to see one that was better built or nicer than a Cent. Most Metros that i have seen have frame splices, weird roofs/ragtops, or fiberglass bedsides that are glued on.. In reality its rare that there are two fourdoors that are built exactly the same. There was very little documentation and there was a lot of experimentation. I guess that means that each one is unique. (excuse my spelling)
Are you in the market for a Fourdoor? A few months ago i went to look at nice Metro in Olahoma, the seller was asking right at $2K for the truck, little rust, but complete, the guy had owned it for 10yrs. I almost bought it, but decided to pass for at least another year before i get another Fourdoor.