This will not be something you will immediately want to accept. The moulded gaskets are really intended for valve covers similar to those on a 5.0 Mustang, and some of the after market Ford Motorsport valve covers. They (the 5.0 covers) have somewhat of a "rolled over" outer edge on the gasket mating surface that helps contain AND seal the gasket. The type of valve cover you are using are milled flat (assuming it is not warped) on the gasket surface and is intended to use a flat gasket. Get a high quality cork gasket such as that made by SCE # 136076 or Fel-Pro (High Performance Series # 1645). Both are 5/16" thick. The SCE's have the little locating tabs, the Fel-Pro's do not. Use a contact adhesive (such as 3M or Permatex weather strip adhesive in a tube) on one side and attach them to the valve covers after cleaning the suface with carb cleaner or lacquer thinner Put a small ring of adhesive around the bolt holes of the valve cover.. Let them set for a few minutes and then install the covers with the gaskets attached to the heads dry. Be sure to wipe the mating surface on the heads clean of
oil before intalling the covers. Snug them down. Start the vehicle and drive it a short distance (4 or 5 miles) just enough to get everything hot. Shut it down and recheck the bolts, they will need to be snugged down 3 or 4 more times untill they take a firm "Set" and compress as far as they are going to. This takes a few heat cycles. They will NOT leak if you do it like this. But be forwarned .....the cork will relax and the bolts will be loose until the heat cycling causes the cork to firm up. You may even want to use a little locktite on the bolts after the gaskets take their final "Set". I experienced a leak myself until the heat cycling took effect. This procedure has worked well for me. I would encourage you to use studs instead of bolts.