Carb issues - flange and jet needle

[Husker45]

Moving onto the carbs on my never ending engine rebuild (cb77E-212739) I put the flange onto a surface plate and it is no where near flat. I can get a 0.50 mm feeler gauge under one side. Is it ok to remove this much material to get the flange flat? Also my needles are part number keihin 24301 (note the 1 is mostly a guess as its hard to read). Is this the correct part? The needle seems to have a slight ridge on it where it sits in the jet. Is this etching and is it ok? I know parts are hard to find and I want to reuse as many as possible. As always thanks for the advice.