If you are pulling the oil pan and valve covers, take the time to check the edges for flatness especially around the bolt holes. If they aren't completely flat a small ball peen and a little time can get you there.
***do not over tighten the bolts***
I don't know what you are using for valve covers and intake, but if they are aftermarket, check the valve cover fitment WITHOUT the gasket and make sure it sits nice and flush on the head rail. IF it does not, you need to remove small increments on the valve covers where it might be hitting the intake, until they do.