Wanted to take a picture before mentioning this. Take a look at the picture of the N.O.S. bowl in the link below. There is what appears to be a line all the way around on the gasket sealing surfaces, both external and the internal venturi area. This line is actually a "ridge" which "bites" into the gasket and aids sealing. Milling, filing, or sanding will remove the ridge in the effected area, and will provide worse sealing, even if the mating areas are perfectly flat.
www.thecarburetorshop.com/Rochestersealingridge.jpg Jon.
