Charging questions

I just bought a 1971 dodge dart. It is a 400 big block in it. the last own put fog lights on, after market stereo, electric fan that pull alot. so far through the day havent had a problem with the charging system. took to a cruise night tonight. at stop lights or stop signs with all the lights on and the fan running. the car idles down and dies at stops. i have to remove the fan relay to get started because i dont have the power to turn it over otherwise. Thinking that i need to install a larger amp alt. if so what amp do i get plus i red something about having to remove the stock amp gauge because of fires!!!! Well how the hell do i do that? Plus should i install a switch on the fan?