I have one of the Lyman New Model Army pistols purchased in 1978. The pistol has seen heavy use and countless hundreds of rounds. At one point in the late 80's I managed to stretch the frame using alloyed lead round balls and Pyrodex. It stretched enough I opened the gap to about 1/8" and it wouldn't lock up. I was able to hammer the frame back into shape (it's pretty soft, as are all of them) but in the process ended up having to shorten the barrel by 2 inches.
At first I didn't think there would be a remote possibility of parts interchanging with a contemporary Uberti but I swapped the cylinder between the two and the results are promising. The Uberti cylinder worked as would seem to be normal in the Lyman, rotating and locking all the way around. But...the Lyman cylinder in the Uberti didn't want to allow the hammer to lock at full cock. That tells me there's enough difference in the ratchet cuts to possibly cause issues.
Lyman on top:
Even though the Uberti cylinder locked up well in my particular Lyman, I'm not sure the same would apply to another copy, then there is the question of whether the chambers align to the bore when locked at full cock.
It would need to be confirmed that the Uberti cylinder is centered up on the bore and measure the two cylinders to see how close they are as this will affect b/c gap. So in the interim I'd say "promising" but not assured. This weekend I'll take a closer look and try to post back on those aspects.
If Uberti did make those for Lyman, they changed the frame design slightly since then...particularly the cut out that exposes the barrel threads. The new Uberti's are much more true to original than my Lyman copy is.
Lyman cylinder on left:
