I have a 1" X 32" X 1:70" .58cal Flint barrel on it's way from them for a TC Hawken stock right now but that doesn't answer your caliber specific question.
I can tell you that I've bought and used a .62cal smoothbore drop in Flint barrel from them and it works perfectly...so based on that, and their barrel reputation in general, I fully expect the .58 RB barrel will be fine.
Note: I had to remove the underrib and trim off a 1/4" of it's length as it was a tad too long to drop down in front of the nosecap on my Hawken.
And it also had black thimbles which I had to replace with brass ones to match the Hawken furniture...and it had a black tubular aluminum ramrod with chrome tips which I replaced with one that looked more traditional on the Hawken