I guess Jim Clark and his heirs are a little wilder than correspondents here. From the current Clark Custom Guns catalog:
"Weld hood and lugs on factory barrel & prep for fitting $ 60"
That used to be standard practice before the cottage industry of oversize replacement barrels got going. Doesn't mean just any welder can do it, but the local guy who did one of mine had no trouble and his Daddy the gunsmith fitted it up to shoot very well.
As to the Swenson locator lug in the slide, he may not have been the only gunsmith to do it, but there weren't many. Most just fitted the barrel tight. But if you want one, the only reason not to do it is that there are people who will pay enough for a Randall to set you up with a current production gun.