Looking for advice/gunsmith recommendation for some rifle work. Specifically tapping and drilling holes in receiver to correct misaligned factory holes.

Before you go that far, I'd suggest you try a couple things, if you haven't already. First, what kind of scope base are you using? Single piece mounts can be adjusted for windage. If you've looked at that already then I suggest using a set of Burris Signature rings. They use plastic inserts that can be turned to adjust windage and/or elevation. Finally, I'd suggest custom bases. Your gunsmith can correct alignment errors caused by misaligned holes by machining the bases to align with the bore. The last thing you want to do is weld and re-drill.