First, I would ask myself if the dominator info came from a reliable source that has experience with this intake or is this just some nutball that thinks he knows and has convinced you.

If it is determined that the Dominator is the way to go, isn't the top plate just a flat plate that could be replaced with another top plate fabricated from aluminum with the Dominator bolt spacing and holes and then bolted to the manifold?

As far as hogging out an existing carburetor, call these guys and ask if they can do it. If not, ask if they know who can.
http://www.braswell.com/prod_catalogs/prod_cat.htm