I've only used the H&R factory program for barrels on H&R/NEF firearms. Some folks have bought them from individuals, mounted them, and never had a head space issue. I would be wary of that since I don't have a way to measure head space other than the shade tree way.
When I had a collection of NEF firearms I did enjoy the interchangeability of barrels. I had the .50ML, .243 Win, 12ga turkey barrel, and .410 barrels. I would have kept them and added more barrels if Marlinitis hadn't come into play.
Of the 50 to 60 some H&R barrels I've owned about half were bought used and fitted myself, sometimes they fit fine with no adjustment or fitting necessary, most require a little fitting of the latch engagement, some require major fitting to include cutting or shimming the pivot. At this time I have over forty H&R/NEF rifles and a few shotguns. H&R will fit used barrels if they can if you aren't confident in trying it yourself, how to fit/check is covered in the barrel fitting info in the H&R Forum FAQs sticky, link below. Hundreds of barrels and frames have been sold in the H&R Classifieds at GBO, many members buy used barrels and fit them at home, many others buy em and if they don't fit, resell and try another barrel, those that have several frames so they can try several to check usually have a frame that will work fine. Many gunsmiths will fit barrels as well, my smith who does rechambers and rebores for me has fitted many barrels for other members at GBO.
Good luck, I've never ever seen an H&R or NEF RIFLE barrel on Numrich, only shotgun barrels, they would be listed under NEF, Numrich is a little behind times, H&R hasn't made an NEF branded firears since 2007! Keep and eye on the GBO H&R Classified forum, a 45-70 barrel just sold yesterday for $130 shipped.
Check to see it you have someone else in the business of making transfers, I pay $20 or $22 for my transfers. Bud's has a list of preferred transfer dealers. There are others that you'd have to contact and verify they are still licensed and what they charge, the list isn't always current.