In many cases, yes a .45 cal cf barrel would be suitable for conversion. Look for one in a .457 groove with .451 lands and a 1:20 or slightly longer twist. That would make a great .45 heavy conical BP barrel. You could probably ask Ruger which of their factory barrels might meet those criteria. I know they made some barrels for a .45LC at one time that might also work. As you can see from the pic, I've thought about that very mod. Cecil Epp has plans to do a Ruger No. 3 so you might touch base with him. Cecil and family are PRBULLET.com - he has already done some similar mods so might be able to give you some pointers. Seems a pretty decent feller.