You could try the Dealer. They're about $250 each. They are the original Firestone air springs that lasted ~10 years.

For aftermarket. I would recommend Arnott for quality, only because I'm not familiar with Suncore. I have Arnott parts in service that are 7 years old with 0 failures.

Rememer, "The price of quality parts is forgotten long after the warranty runs out". Buy the cheaper ones, but plan on replacing them again while you own the truck.