Besides needing a 3" mag chambered bbl, one has to do something with the ejector. It's complicated and I'm no smith, so I'll leave it alone. A gunsmith bud did one of mine a while back, but he owed a favor.
IMO, you should leave that classic as is, and get a 3" mag when you can find one suitable. Also, with the new alternatives to steel coming along, the need for all that payload space is a bit diminished.