Ah, the joys.......
What I found best to seal the manifold ends on the W5's is to use grey silicone sealer on the spacer to china wall, I also drilled and pinned the spacers so they wouldn't move, and I used the factory magnum style intake seals (they are metal and rubber) on top of the spacer also drilled to accept the gasket tangs, with silicone sealer on both sides of the gasket. I haven't had any leaks since I've been doing it that way.
How was the fit on that intake? Did you have to do anything else besides relocate the bolt holes?
Oh and BTW, I use ARP head studs and never retorque, no problems yet with the FelPro 1008 gaskets and 12.7:1.