I use the 3M yellow trim cement ("Gorilla Snot" if you happen to be a NASCAR wrench). Put a thin layer on the block and the underside of the end gaskets, let it dry fully, and it sticks to itself when the gasket is applied to the block. Use a little dab of RTV sealer where the end gaskets and the side pieces come together, and some Super 300 around the water ports, front and rear. DO NOT use any sealer around the intake ports. I've seen my competitors on the race track use a straight bead of RTV instead of end gaskets, but I'm not fond of that practice.
Manifolds that have been milled to match up with milled cylinder heads can have some pretty serious gasket fit problems, and troubles with vacuum leaks, so a lot of special attention needs to be given to anything that's not factory stock in the block/head/manifold machining area. I used to angle-mill cylinder heads for better race performance, and the intake had to be matched to a specific set of heads and used as a set. This was done on 350 engines that produced upwards of 600 HP at 7,000+ RPM, not anything that got run on the street!
Jerry
