Best Gearing for 8 3/4 Behind 1970 Duster 318

Hello,

Recently purchased a sharp driver quality 1970 plymouth duster. Car has 318 with Edelbrock Intake and Holley 4 Barrel Carb paired with 3 speed 904 trans and 8 3/4 rear end with non-posi 2.76 gears. Rear tires are 255/60/15 and front tires are 215/70/15.

I am planning to convert the rear diff to sure-grip and upgrade the gearing. I am considering 3.55 or 3.73 and plan to mostly drive car in town but will occasionally want to drive short distances (30-45 miles) and would like to be at highway speeds up to 60mph.

Curious to hear if anyone has built a similar car and has experience with a build like this?

Thank you in advance.