360 to 408

I am doing my first build. Picked up a running mild 360. It needs a rebuild before I put it in my car. My intensions are to go from 360 to 408 because I have heard nothing but great things about power/cost of the 408. I hope to get anywhere from 450-500ish hp out of it. What do I need to make this happen? I should say that I will also be running pump gas and eventually adding a 150-200 shot of giggle juice down the road.

I am also thinking about a 4-speed automatic because I live in the country and would like not to kill my engine. can anyone steer me in the right direction there as well?