Sunday funday and another oil leak!
Do they hit in the front and back?
I have a set of covers here that need modified to sit nicely, they hit on the intake runners.
Put the cover on without the gasket as mentioned, mark and grind the cover until it sits firmly on the rail, then install the gasket and cover.
When I install covers, I usually use the cork gaskets, never had an issue with them. I put a little RTV on the cover, put the gasket in place and let it sit for a bit, when I install the cover I use a thin layer of grease on the head side. That will aid in the gasket not sticking to the head, so if you need to pull it to adjust rockers for instance, it's a clean process.
Do not "over torque" the bolts.