Need guidance on getting 340 running again

Here's what I would do. Just going off what you say since the car is not in front of me.
Drain fuel. Disconnect fuel line on both ends. Blow air through line. If clear reconnect. On engine side connect fuel filter prior to pump and one after. Refill tank. Once you've had engine running through a tank or two change filters.
Change oil and filter. Pull dist. and prelube engine. Assuming you have tool for that. If you feel ok with it can always disconnect coil wire to prelube with starter.
Pull and rebuild carb. It's probably full of that dried up fuel crap everywhere. Check all rubber fuel lines; may need to replace.
Install your new wiring harness. Personally I've never liked those MSD boxes; assume that's what you have. I just use an old chrome box with an old school Mopar elec ignition setup.
Probably alot more than this but can get you started. Check brakes and fluid is a must as well. It's been sitting. They don't like that.