M1 Single Plane Question

If its really rubbing you the wrong way, pick up some good 2-part epoxy putty, make sure its REALLY clean(cant emphasize CLEAN enough here), put your spacer on, and fill the gaps between the spacer & the top of the manifold, then go in with a die grinder and smooth out the transition. This used to be a standard part of prepping an intake. Nowadays everyone figures you just bolt it on & run it. If you are using the Wilson four-hole this wont work as the joint wont be easily acessible.

Just by the tone of your post, I think you also need bigger shooters, but I might be stating the obvious here.