Iam in the same boat with my guide gun in that I want to use a extended eye relief scope(leupold 2.5) and after looking things over, I might get the barrel drilled and tapped for bases. It would be possible to use the existing bases that fit on the reciever but I was thinking of getting bases that the thompson encore system uses since the bases is rounded and would fit the barrel better. Also plan on using quick detach rings so the scope can be removed. I also have the peep sight on mine so I would be able to use them also.
Keith