As far as I can determine, their were only seven transition Henry's ever built. No two were alike. They wound up becoming the "Improved Henry" or the 1866. If one can't find someone willing to part with a Uberti built Transition, building one is expensive. The easiest way to do it, takes two rifles. An 1866 and a Henry. Take the forearm, barrel and mag tube off the 1866 then sell them. Remove the forearm lip off the 1866 frame. Remove the barrel assembly from the Henry, throw the frame away and do the necessary "fitting" to graft the Henry barrel to the 1866 frame. From 6 feet, it'll look just great. But ...... Real Expensive.
Coffinmaker