You can do either. A 5071 trigger will drop in after a bit of wood removal. A 5018 can be used with a few simple modifications. The 5071 is just a modified 5018. Neal Stepp can do it for you if you buy a new 5018 from him....he did it for me and that trigger is on a 1974 1411. I use it as a two stage and the second stage breaks nicely at 2 ounces. There is a guy, I think in CA, that will rework your existing trigger to about 2 ounces. A search here will locate his name and address. I have no experience with him. bob finger