Floodgate, you might want to look at Live Steam magazine or any of the two sister publications. Think a place called Blue Ridge or something similar may well sell the british pipe thread taps and dies.
Bigjohn, stumbled across a potential problem with the cadet bbl. Just for the heck of it used a dial caliper like a depth guage and from the throat to the barrel breech face I got a reading of 1.300 and from the chamber it looks like there was a reamer run in for what looks like the 32-20 case. I'm going to double check later today, too bleary eyed and this old guy needs all the beauty rest he can get. I slugged the bbl so will have to play around with it, and see what dia. I need.
This project seems to have taken on a life of its own. Frank