Because having your cake and eating it too would be not using worthless 3.55 gears with an OD. I'd consider 3.91s the absolute minumum. With 3.91s, your ratio in OD would be 2.69.
All depends on individual tastes and goals Rusty. I drove a lot of miles in my Challenger with a 340/non lock up 518 stock mopar hi stall converter/3.55 and loved the combo. I want to cruise 80 on the interstate and not go deaf. That combo would do it at about 2800 rpm. Not sure what I will go back with until I figure out the entire combo but 3.55 or 3.73 are likely.
