I've used Kart barrels in the last two 1911s I built. I've used Wilson, Ed Brown, Bar-Sto, Les Baer, and Clark too, but the Kart is the best I've seen. The non-ramped Kart kit comes with a pre-fit match bushing, barrel link and link pin. It is not a drop-in and does require fitting the sides and end of the hood. Easy instructions are included. A few minutes with flat jeweler's file is all you need to do the fitting.
Be cautious of "drop-in" barrels. If they are made to fit a variety of guns, chances are they won't be a good fit in any gun. There are 6 points on a barrel that need to fit well if you want decent accuracy. The left and right side of the hood (lock the rear of the barrel horizontally), the end of the hood (head space), the link (rear vertical lock), the bushing-to barrel (front barrel drift), and the bushing-to-slide (bushing drift). When all 6 of these points fit snug, accuracy will be best and malfunctions will be minimized.
When a barrel is properly fit to a slide, the top end behaves as a unit, thus the slide to frame slack has minimal effect on accuracy. With a loose fitted barrel, a loose slide to frame fit will compound accuracy problems.
Brownell's sells all the above barrels and a few more.