If it were me I'd probably go the tap route first with the tap and some oil. Once threads are boogered up bad though, it's usually a moot point. Since this is a cast frame, you might consider checking the Handi Classifieds for an inexpensive SB1 frame. I've seen them as low as $45 shipped and then you can see if your barrel fits on that frame. I don't think the helicoil will take in cast metal frames very well, but you never know. Maybe some others have better ideas. Only other thing I can think of is boring hole larger and epoxying in a Rivnut style fastener or smooth sided spacer nut into the hole. 8(