As David suggested, I contact cemented a piece of .035" steel shim to the front of the barrel extension lug, where it would contact the rear of takedown lever (first pic). I assembled the parts and checked it for proper function. Everything works like it should, so this modification [repair?] should be do-able. Second pic shows the barrel extension almost level with the front of the frame. I think .040" would be just about right on.
