Both 20" 243 barrels are Superlights, one has sights, one doesn't, you'd best use a 22" barrel since the Superlight barrels couldn't be rebored to .358" and have enough barrel wall just ahead of the chamber swell, I'm contemplating having one rebored to .264" for a 260 Rem and having doubts that even it won't work, the barrel is only .750" just ahead of the chamber swell, waiting on Wayne York's opinion now.
I think all modern and possibly ALL 357mag barrels made since 2000(Marlin) have been the faster twist, both mine are, one was made in 2007, the other long before that, I bought it in 2004 as a 357Mag that had been hand reamed to Max, then rechambered it to 35 Rem. You can check the twist rate using the instructions listed at the bottom of the twist rate list in the FAQs. H&R shuts down sometime in late December until the New Year, so figure that in, but barrel fittings for in-stock barrels has been running about a month, see the Ilion Poll sticky.
Tim