I found a base that worked for my needs. It's a weaver 63B which has a flat bottom.

As I said in the original post, my barrel was already tapped for other scope rings. So I just used the existing rear hole in the weaver base and aligned that to the rearmost tapped hole in the barrel. Then I had my machinist drill me two more holes to line up with the other holes that were in the barrel.

The rear site stays where it is but obviously I won't be using it with this setup.

I have already checked my scope to be sure that it is high enough not to interfere with the hammer and that I can move the scope back far enough to get my needed eye relief. All is good.

I am using Weaver extra high rings but I can still get a nice cheek weld with good eye relief and the scope does not feel too high.

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