Gear Ratio

I'm taking the pig unit off of the 8 3/4 rear end thats in my 340 Dart.... I'm looking for a new set of gears with a posi unit.... what gear ratio should I go with? 3.55? 3.23? 3.91? any others? I'm just looking for opinions and some feedback. My car is a stock 69 Dart 340 3-speed with modified axels to run 265 tires in the rear.

Thanks