The first pic below is from the accessories brochure, showing the original roof rack. The second is the aux. battery wiring diagram, printed in '78.

Here is the Bentley wiring diagram for a 1977 bus.

Mark Dearing brought me a few nice things to scan at High Country. Below is an original '77 window sticker and the dealer installation guide for the optional air conditioning unit. There are all very large files when clicked on so you can print them for your reference.