Oh, I thought you were after the stake beds, specifically. Not a ton of hot rods with flat beds. Pinkee's built one back in the 80's, but I think it was a Model A or 34ish.
Seems I’d remembered seeing some 53 through 56 lowered with flat stake beds on the back but I could be wrong. The bed on my truck is shot and a new one’s pretty expensive so I was thinking about building a flatbed. It would also be fun for cruising with people in the back parades beach, etc.