You got me beat on barrels. Looks like you have a lot of MkI/VII barrels.
I have two Mk XIX's, one in 50 with both 6 and 10 in barrels as well as 44 barrel in 6 and 10 inch.
I then have a 2nd one in 357 with 6 and 10 inch barrels. I keep it dedicated to 357 so I do not have to swap the bolts constantly.
Technically my 50AE is a MkVII, the caliber is stamped on the slide, not the barrel, but it is identical to the Mk XIX.
The 357 is a true MkXIX.
I did just add a MkI to the lineup. It came with a complete barrel and slide assembly in both 357 and 44. Both 6 inch.
If you think finding the 10 inch barrels is hard, you should try finding the 14 inch.
That is my current plan for my MkI, get 14 inch barrels in 44 and 357. I would be happy to pay $750 for one of those barrels.