Oil weight/type for this car

Those are getting somewhat rare as most people ripped the 6 out and stuffed in an 8, the stock ones are becoming collectibles these days.
I would change all the engine fluids, battery, starter may be fine. I wouldn't change out everything until you at least get the engine running. Nothing like replacing a lot of parts only to discover it has a rod knock or other internal issue.
Oil wise plain old 10W-30 non-synthetic is what it should use. Make sure you can turn the engine over by hand with a wrench before doing anything else. A locked up engine could be rusted internally from setting. Usually you can feel that because the engine won't turn or it will have areas where it turns real hard. If you can, get one of those cheap inspection cameras for a phone or laptop and look into the spark plug holes before hand. That can make it easier to go farther if the bores are all clean and bright.

Hello, I'm Danny.

Just to add to this question a big concern is having old fuel and moisture sitting in the fuel tank, fuel filter, and fuel lines throughout the entire fuel system. Also, from sitting it's possible the mechanical fuel pump might have a rotted diagram from years of sitting. After following my colleague Steve's advice from the prior post after determining if the engine does turn over freely, The battery is fully charged and functional and you are ready to fire up the engine I would find an external source of fuel to test. A fuel tank and system sitting for so long might be not so functional. Even with fresh gasoline it still might try sucking years of corrosion, debris, rust flakes, etc through the fuel lines and filter which could clog and act like a no start condition. That's if the mechanical fuel pump still actually works. You might just want to use a small amount of gas in a small container and pour directly into the carburetor. To add again to what Steve said I also would hate for you to put time and effort into something that is beyond salvage. Unless, This is a cool project you want. Hope this helps and thanks again for using 2CarPros.

You're welcome.

Let us know how things turn out and hope you will use us again in the future. Thanks again for using 2CarPros.

Danny-