Welcome aboard Mike!
I would check that the spindles can be turned by hand and if so grease them up before putting a belt on it. Look at the spindle pulleys and make sure they are not rusted up or have sharp edges that will kill a new belt. Also would be a good idea to look at the underside and make sure there is nothing tangled up in the blades and that everything is intact and tight. When you find a deck missing a belt, you gotta figure it is missing for a reason just to be on the safe side.