I swapped a 4:10 rear behind a 250-6, for a 350 SBC and 3:08 gears.
I did an entire rear end swap from a salvage yard because I know entirely zip about setting up lash.
Just how fast do you plan on cruising through town?
A 350 CI Small Block Chevy built with torque in mind won't be blocking traffic if you don't want it to.