O estimable crafter of pine boxes,
It's probably me who's all wet. Now that I think about it, I don't have any knowledge of Colt factory conversions in the Henry cartridge. I recall seeing an 1860 that I believe was converted to the Henry, but now that I think about it, I think it must have been a gunsmith special because I believe it required removing the barrel to reload.
Colt did, I understand, produce some SAAs in .44 Henry, but of course those aren't conversions.
Is the .45 Henry Flat different from the .44 Henry Flat?