I decided that I couldn't stand having odd ball bushings in my Girsan MC1911S. I could easliy have just made the grip screw holes larger but I'm hard headed. I purchased a .236X60 tap from Midway and some bushings and screws from that online auction site.
First I must say that this is not required and there is a chance you could mess up your 1911 and have a skeleton frame... I was fortunate and it turned out great.
First, I made sure the frame was level by adding a shim on the bottom. In my case I just used an izula kydex sheath. I removed the bushings and drilled the holes out with a 7/32" metal drill bit trying to keep the drill in a near perfect square position. It might also be smart to put something in the clip area to keep from busting through the hole and marring the other side. Once the holes were done and my heart beat returned to normal, I used the tap to re-thread the holes. I used the low position on the drill and went slowly. Make sure the bit is in tight because reversing it out can break the bit free from the chuck if loose...
Next, I screwed all the bushings in place for test fit. I think later on I may remove the bushings and blue the threads with perma blue and a q-tip for some rust inhibitor. Also, I may ad some blue lock-tite.
After all this I checked to see if my grips fit and fortunately they did.