Welcome to the group. Arnie and I have an 87 Grandby on a 78 Chevy C20.
First, what you have there is Unobtanium. :)
Second - we're gonna need more pictures and a story on the find!
If you need to see a manual, we copied ours (came with the camper) and put it on Dropbox.
2017-07-18 FWC
You're...