Just sitting for the past 39 years, it’ll need an overhaul since as mentioned, the belt is cracked, rollers have flat spots on them, rear panel has rust from sitting in a damp area.
It’s like finding a 1985 Ford LTD Crown Victoria that was driven for a couple hundred miles, then was parked for 39 years. Some people think they may be getting the deal of a lifetime but in reality, may not be a good deal after all since all the rubber hoses and seals as well as gaskets will probably be dry rotted from sitting for many years. Probably better to get one that has been driven, but everything in terms of maintenance and general items were replaced at the recommended intervals or replaced every so often to keep things in tip top shape. Sometimes, low mileage items can have more issues than something that’s ‘high mileage’ and taken care of.