Others may disagree with me, but I would just siphon out what what you can if the tank is full, and then add 6 or 8 gallons with a gas can. It is a lot less work. If there is not that much gas in there, I would just top it off (to dilute the old gas with fresh stuff) and go.
My truck was down for 8 months recently, and the stock 305 ran great on 8 month old gas. It is just an old 305, though. It will run on anything, kind of like a lawn mower, but with fewer horsepower.
Slonaker