model 12
For the most part they will interchange with the exception of the adjusting ring and the chamber ring.
There are notches on the adjusting ring to tigthen up the barrel to receiver fit, there are 5 different ones for this depending on the wear of the surfaces, the ones i see now have no numbers on them so it's up to somebody who knows how to tell which is which.
The chamber ring is a nother issue in it's own, you could get lucky and it will fit up good, or you will need to line ream a new one and set headspace, there are special reamers for this to do it as one piece, it's best to do it this way because if done wrong, the fired shell will catch on the part that swells around the chamber ring and you will have to beat the gun open.
Because the barrel you found is not where you are, and there is no way of checking the fit first i would shorten the one you have.
If you need any help let me know, you can get me in my shop.