I bought a pair of aluminum finned valve covers for my 69 327 with 350 heads, edelbrock rpm intake. They wont sit down on the gaskets all the way because they slightly touch the intake runner boss. Is this why they make thicker gaskets. Is this common with the aluminum v.c.'s or are they too wide and I have to put a bevel on them.

Do you have a picture ???

I've seen this before. The v/c's have a lip around them as a stiffener. Use thicker gaskets and you should be fine. If you cannot find them, glue two sets together with high temp silicone gasket maker. I still prefer the cork v/c gaskets. I use 6-8 dabs of silicone on the valve cover side and none on the head side. That way the gasket comes off with the valve cover and not stuck to the head.

You could always do what Chevrolet did and grind away the area where the casting hits the intake manifold. Chevrolet did that waaay back on the Corvette cast aluminum valve covers. It's not like you need to remove the whole lip, just do it in the short area where it hits the intake.