Its called the 400CorBon, and all it takes is a barrel (and sometimes a recoil spring) swap in a pistol chambered fro .45ACP. It uses the same magazines as well.
I custom built a 1911 a year or so ago just for the purpose of having a 400CorBon, but you can buy the conversion kits pretty inexpensively. The only thing you need to worry about is that some gun manufactures such as Kimber use inheirently inferior MIM (Metal Injection Molded) parts in some of their weapons and they may not be able to stand up to "full house" 400CorBon loads. Its best to substitute forged pieces for those anyway.
How do you like it? What kind of numbers does it run?