I realize you're working with forged, billet aluminum, not cast aluminum. But I don't think a factory ford casting is proof that it's not needed. Looking at a current ebay auction for a Keith Black block (water), you can clearly see that they think the webbing is a good design feature. Besides (I did notice you skipped that question), if you can produce a tall-deck version then the webbing might become more critical as the manifold to head junction will most likely have a spacer plate in it, weakening whatever cross-connection you (and the factory) may rely on to substitute for the webbing. Plus, I think you may want to look at the newer versions of the mod block, they do have webbing in the "lifter" valley area.
