nos on a 318

I'm thinking about doing a 125 shot set up on my engine and was wondering what do I need to do to the engine to set it up for nos... Will it cut the life of the engine in half, how much improvement will this give me.

I currently run 14.8 but I'm hoping I can get high 13s with my new top end I'm going to be doing... And then add a 125 shot do you think I could. Hit 12s.......