Dual carb head are only work with a dual carb block, as the valves are backwards, and because of that, it uses a different camshaft. Also there are no reputable machine shops within 250 miles of where i live that i know of. I really think that some sort of epoxy is my best bet at this point, I am just not sure.
Also, to have the holes filled back in, i would have to remove the heads, right?