Kenny.  Nothing wrong with grinding but without the right tools or sharp carbide cutters it can be labor intensive.  A milling machine is obviously another method that allows the carb holes in the ‘B’ intake manifold to be quickly bored to the desired size.  I see where you’re just a bit further than a hop and a skip from me but if you can get that manifold over to me, I can bore the holes out larger if you don’t find someone in your own area that can do it.  It’s also a simple matter while the intake is in the mill to lower the pad ~3/8” or just enough that you have a nice flat surface without the cavities that are already residing there.

Here’s a pic of an intake where the throttle openings were made oval and the carb flange itself taken down enough to give a more adaptable sealing surface.  I thought there was a picture on this site of the holes being bored larger without the slots with the mill but I didn’t find it doing a quick search.