Keep blowing intake gaskets...

I'm also running a 5.9 magnum with an Edelbrock Air-gap intake. The intake gasket kit I used is OEM replacement (Fel-Pro from Autozone) for a magnum engine and it came with rubber seals for the end rails so I used them. The only rtv I used was on the corners. Been driving the car pretty regularly since July and haven't had any issues.