Do a search for GM ST33085, that should be the GM Shop manual for the 1985 GM motorhome models. It will cover all the various chassis elements specific for the van bodies configured for motorhomes minus any of the coach parts. Example, on mine the manual show the rear taillights terminating at a plug behind the drivers seat. This is where Winnebago connected it to the coach's harness for the rear lights. To find out where it went from there, I need to use the Winnebago's wiring harness for my model.
So, as others said, if you need the chassis manual (based on the actual chassis year not just the RV's year), any manual for and installed equipment like a/c refrigerator, converter, etc. If you're really lucky, you may also be able to find the actual coach manual.
