Ron
My experience with drop-in barrels has been kind of the opposite. Years ago I had a Colt National Match barrel and bushing assembly that I bought at a local gun shop. I believe it was from Colt's Custom Shop. The bushing, barrel link, and link pin were already fitted to the barrel. I used it in several different 1911s that I had, including a nickel plated Colt Government from the '30s, that turned it into a veritable tack driver without any additional fitting required.
I have also used drop-in 9mm. barrel assemblies in my .38 Supers with similar results, though not quite as accurate as that National Match barrel was!