The old stock screws were Philister head screws and can sometimes be found at good old fashioned hardware stores, or specialty fastener suppliers. And yes, I spelled that correctly. Philister head screws will have a Phillips type cross in them. Back plate gaskets are cork but can be easily made out of any kind of thick, soft paper gasket material found at auto parts stores. Head Gaskets are a soft aluminum, and they can be cut by hand with a sharp knife and repeating cuts. Cut the ID first, and you can cut the OD with sharp scissors even. Not that hard to do if you really need them, and practice makes perfect.
Type at you later,
Dan McEntee