Time for a re-build

The Long bike is due for a major overhaul again, this time I don't know if I can save the frame.

The problem is that the thread in the frame where the bottom bracket screws in must be stripped. The bottom bracket has all but broken free of the frame but I cannot unscrew it.

I've looked around for a second hand replacement frame but haven't been able to find any suitable donor bikes. Mountain bikes these days seem to all come with suspension on the front, I need more rigidity.  If I can't re-tap the thread for the bottom bracket, I am really going to need a suitable steel frame with rigid forks to transfer the Xtracycle onto. I never thought they would have become so hard to find.

I don't intend to start this fix until about April or May when the weather improves but I sure hope I find a solution before then. I doubt I'll be satisfied with another frame so I'm starting to think I aught to ask around at some engineering places to see if it's possible to insert a sleeve and re-tap the thread.