I think it's time to change valve cover gaskets again on our '78 L48 pace car. Just curious as to what you all have had the best success with.  What company,  Just plain gasket, cork, cork with reinforcement layer, rubber, with or without  any sealant?  The hold downs are a spreader bar maybe 5 inches and the small capscrew with no lock washers or the like.  Thinking that lock washers should be used.Thanks

Thick cork w/metal reinforcement, or plain cork. Fel Pro brand.
Steel cover = Spreaders w/NO lock washers. Aluminuminum covers do not need the spreaders nor lock washers. Flat washers would be otay, tho.
NO sealant.
Make certain the covers and heads are absolutely clean and dry.

I used the Felpro ones that look like they are cork with a blue coating on the sealing surfaces.  No leaks yet and I use synthetic oil.

I have used both fel-pro rubber reusable and thick cork. The rubber gasket were on for less than 1000 miles they were hard and brittle from the excessive heat. So much for spending the extra money on reusable gaskets that are not reusable. The second set I used was the thick cork gasket. They cork gaskets of today are so much better then 20 years ago. I prefer the thick cork over the rubber any day. I bet there is a better chance of reusing the cork.

Mr Gasket. if you have the aluminum covers  clean them well run a small bead of ULTRA black silicone set the gasket on and let it set up. when dry wipe the exposed surface with some motor oil. and tighten them down. doing it like this allows you to remove the valve cover without damaging the gasket. if need be. the secret is "CLEAN" 

I have reusable rubber because mine is a new engine and I have to re-torque the heads at specific intervals during break in.  I don't know the brand because they came with the engine. I do make sure everything is clean before I re-install.

That's a new one!
I cringe when folks use any kind of "sealant" on a cork gasket....but...if it works for you, go for it! I get the main point of "let it sit up"...that's a big factor in making it work, and not slide right out, but who has time for that?

Using oil on the gaskets before bolting the covers on is something I have never heard of, or done. I have heard of some folks using "Pam" cooking spray....like racers that remove covers every few minutes, but for a driver? Hmmmm...neat trick.

actually super weatherstrip adhesive from 3M works better than silicone .

Fel-pro cork gaskets offer 3/32 thick and 5/32 thick. I used the 5/32. I put the bolts thru the valve covers and put the gaskets on the cover. The bolts hold them in place and then I put them on without the struggle of trying to make sure the gasket doesn't move. No sillycone for me.

Thanks to all that have responded to my valve cover question.  Gary C