My son just sent me this link from "Truck Camper" magazine about 1969 campers.
https://www.truckcampermagazine.com/...r2SLs360i4OsP4 . It shows Chevys, GMCs and the other brands with campers. Here are some pics with the GM trucks. I think I saw a thread about a week ago with some pictures of a service body that looked similar to the one in one of the pictures.
Are you there Jocko?