8 3/4 Sure Grip ratio change

In my old 69 Charger R/T SE I ran 3.54 gears in a Dana behind a 440 and 18 spline 4spd. trans with 275 15 tires and at 60mph I could nail it and break my tires loose. I would have no problems running 3.55's in my small block Barracuda at all and that's what I am going to run soon as I get the 7 1/4 out lol