A drop in fit beavertail safety would be goal #1 .... and a commander hammer would be a good addition also. Here is a link to a Wilson drop in beavertail so you wont have to order a jig and cut your frame.
Great, wont let me post a link. Anyway, you can go to Midway USA, Brownells, about any major supplier and find one... or use a search engine ( Yahoo, Bing,Google) Brownells parts number 965-429-100.