Which is the better manual to get? The Fisher Body service manual or the assembly manual?

 

You need both. Different info in each.

 

Both.

 

There are THREE manuals that you need.

Chassis Service Manual - covers all the information needed to maintain, repair, and troubleshoot the mechanical and electrical systems of the car
Fisher Body Manual - covers all Fisher-provided items (body, doors, glass, trunk, power seats/windows, interior upholstery), including the electrical part of those power options
Product Information Manual (aka "assembly manual") - this is a compendium of the factory engineering drawings used to assemble the car on the assembly line. Frankly, the PIM is not really useful for troubleshooting or maintenance. It is mandatory if you are doing a complete body-off restoration and want to restore the car exactly as it left the assembly line.

Note that in SOME model years, the PIM does have info about wiring for options like power windows, console, and A/C. The 1965 version is one example, and unfortunately in that year the electrical info is not in the CSM. In most years, however, that info is not in the PIM.

 

What year PIM do you need?