Virgil: the frame is readily convertable with a new slide , barrel, and recoil spring assy.
The slide is cut for the cartridge head size and the extractor is also positioned according to the dia of the cartridge. You could convert to .40 S&W with a barrel , but the magazines wouldn't be correct either.
You can buy a good slide from Essex arms fairly inexpensively, but would have to mount sites on it. You might also look into the miriad of aftermarket suppliers, from Ed Brown to Brownells and a whole host of others. www.shooters.com has a good list.
The 1911 is a very versatile frame and can be a lot of fun. I have one of my frames fitted with 4 calibers of slides and or barrels. Remember the magazines will have to be bought for each caliber too.
Good luck , and have fun... be safe!
What part of "INFRINGED" don't they understand?