JB, hopefully you have shim washers for the head bolt bosses. They need to be exactly the right thickness to flush out with your milling, or you should spot face to get there. We make some special shim washers for that purpose that we use. I like for the subplate to sit right on the milled area when torqued. My washers are 1.020 x .502 x .142 thick, and we spot face .140. They will embed about .002 when torqued. Most manufacturers' bolt bosses are not machined right-on, although BBM's are the most consistent. Edelbrocks especially need a tune up of the bosses. Just a little info that might save you some pain.........Deck surface to subplate on an unmilled BBM head needs to be 3.560 with my valve length and prep, bolt bosses 3.420 using my shims. That may be different with other valves and prep, but it shouldn't be much different.