The gaskets are the shims, you put as many in as it takes to get a firm but free movement of the ball after you tighten up the flange. If it's to tight you add a shim if it's to loose and falls down you remove a shim. It's explained in the manual.
No, I doubt if Napa or any of the auto parts would still carry them. I'm sure there is something that you need for the truck, there is alway a few parts that you can think of to fill in an order and make the shipping worth while. Try to find a buddy with a Stovebolt and split the shipping.
Denny Graham
Sandwich, IL
