There is no such thing as a ford 302 that does not have a valve cover oil leak on the passenger side! Every single one, no mater what gasket I use. I need beer.
If you are talking about the orig stamped metal type it's probably warped or has had the bolts tightened excessively so holes are puckered(ought to be a joke in here somewhere)... Can be straightened using a flat bar and a few hammer taps...
No leaks here either (Aluminum ford "Boss" style pent roof covers) on the sprint with old school cork gaskets. Your aluminum cover is probably warped or the sealing edge has a nick/gouge at the leak site. Or the head has a nick/gouge at the sealing edge...