The change over btw is $405 total. It's a new shorter barrel and cylinder. They do send me back the old .45 barrel and cylinder and don't offer a trade-in. I asked. The price is the same regardless what replacement caliber. They offer all the usual current calibers as change overs, but not some of the older less known ones, .41 Colt, .44 Rim and .476 Eley. They say this is done quite a bit.
I also want to find out how the barrel markings will change for either caliber. I think I've heard that the 44-40 maybe should say Frontier Six Shooter instead of Single Action Army. I don't know what the 44 Spl should say. I've also made a note to inquire about the front sight for both. And I suppose it wouldn't hurt to inquire what the bore diameter will be.
Whatever I get I'm going to request it be test fired with current Winchester ammo, although I'm doubtful that will wind up being done.
Finally, I'm 90% decided also on Standard "A" engraving and carved ivory grips, which will turn it into more of a display, show piece instead of a shooter. That probably means very little shooting. I'm not sure what that would be an argument in favor of on the caliber selection...