Gear ratio recomendation

With what your trying to do 3.91s as they are a good street gear with performanve in mind. I ran this with my built 346/727 mostly street. 20 to 30 miles daily for a long time and around 18 mpg. New engine is getting 4.30s though lol. (Tunnel rammed 416, with 4 spd is the "plan")