Yeah, if it’s in good condition body and frame, I’d keep it. These trucks are pretty simple to work on compared to anything newer. Parts are relatively speaking rather cheap for these.
Definitely I would try to get your father to give you or sell you the truck. There’s going to be a bunch of work that needs done and it doesn’t sound like he cares very much about vehicles. Don’t want to see your hard work trashed or sold.
Flushing the mess in the coolant system out would probably be my first step. If you have decent tap water, I’d use that for flushing. Ideally pull the thermostat housing and lower rad hose and I’d take a hose and spray in there in both directions until it runs clear. Same with the rad and with the heater core. Flush all of that crap you can put. Fill it with tap water and run it for a little bit. Flush it again. Fill it up with water and a cleaner for coolant and run it for a day or two then flush it again. See how it’s looking.
Full tune-up. Fluids, filters, plugs (double platinum, ideally Motorcraft from a parts store or Rock Auto because Amazon and EBay are full of fake parts), plug wires…
Do a compression test when you do the spark plugs, that will give you an idea of engine health. You can borrow one from a parts store or buy your own compression tester.
