It's easier to convert a Super 38 to 9mm as the shorter ejector of the Super 38 will work with both calibers, versus the longer ejector of the 9mm. Besides the barrel set-up, you would also need 9mm magazines and a slightly lighter recoil spring. A nice set of high visability adjustable sights would help, but not really a necessity for short range work. So if you starting with a 9mm Commander platform, then you will need a Super 38 barrel complete, recoil spring, magazine, and ejector. It makes for a fun conversion package, and gives you two guns for a lot less money.