Need guidance on getting 340 running again

I would start with the basics.

Pull the sparkplugs and put a little Marvel mystery oil or similar in each cylinder and let it sit overnite.

Does the engine spin over(rotate)?

If so move to spark, fuel, and fluids.

On fuel lines I remove the feed line and spray some brake cleaner in the line and use the compressed air pressure to ensure the line is clear.

A shot of brake cleaner also sprayed down the hose from the carb side. This helps the diaphragm in the pump to soften up and pump quicker.

If you have spark, pour a little fuel down the carb and see if it fires.

If so you can now fully assess the fuel lines and carb to verify they are in proper order and make any repair / replacements you feel necessary.