It should be a paper gasket on the base with a cork/ composite/rubber ring around the cylinder spigot. Depending on how long it has been running with the cork base gasket, you may find that the cylinder has a ridge worn by the rings at the top of the cylinder which the rings will hit if you fit a paper gasket instead of the cork and effectively lowering the cylinder!
It may be very slight, but it could break the top ring or create a bit of a clatter, as I discoved when I replaced a cardboard base casket that someone had fitted with the correct paper one. If there is a ridge, get it honed or bored to remove it.
I think you are confusing the sealing rings at the bottom of the cylinders with the paper gaskets that go between the outer diameter of the cylinders and outer mouth of the crankcase. When you replace them use an ethanol resistant material instead of the granulated cork rings which are NOT ethanol resistant. The Spares Scheme can supply them. The paper outer packings can be replaced with a THIN SMEAR of silicone mastic, but the paper ones are perfectly OK.