A while ago I added a Mars mainspring housing with magwell to my MC operator. It took a lot of hand fitting, but now it fits pretty good. I also had to blend the inside flare of the magwell to match the flare that was cut into the frame of the MC operator. It's a pretty smooth transition, but there's still a small gap between the frame and the magwell. I also had to file the top of the housing so that it didn't interfere with the grip safety. Plus I had to use a round file to get the hole for the housing retaining pin to line up better with the frame.
Last night I added a "Cylinder and Slide Super Match Trigger Pull Set 3-1/2lbs". It took a bit of work. Mainly I had to fit the thumb safety. I looked at a couple of resources online about fitting the thumb safety, and it wasn't too hard. I just took it slow and removed a little bit of material and test fit it. Luckily the original safety had a lot of extra material to work with. At first I started with a flat file, then when it was close, I stoned it. I was careful to keep the file and stone square and cut in only one direction. Also, I had to deburr some of the holes on the hammer and sear so that the pins would pass through easily. Finally I had tweak the leaf spring for the grip safety. Everything passed a function check, so it should work well. The trigger feels fantastic.
I bought a new Cylinder and Slide hammer strut and an Ed Brown Rebuild kit. This gave me all the parts needed to change the ILS mainspring housing and the pin for the Hammer strut. Also, I changed out slide catch plunger because the original Springfield version was a little too long. (Which made it difficult to replace the slide catch without using something to hold the plunger in.)
All in all, it was around $300 in parts and some of my free time. A lot of people said it would be difficult to work on a 1911, but I didn't think it was too bad. If you're handy, you might consider it.
Right now, Midway has a sale on the Cylinder and slide set. It's normally $164, but they have it on sale for $130. Currently it looks like it's out of stock, but if you backorder it, you should get the sale price.
www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=816731