question for a rear end mechanic

[keakar]

im looking at the new chevy trucks and it comes with the 3.23 gears and they offer two other gear ratio as well so I have a choice of

3.08

3.23

3.42

for the 4.3 engines

my question is, what gear ratio will give me the best highway mileage because im not worried about losing low end torque since I don't tow anything heavier then a flatboat

so does a lower gear number mean more low end torque or higher highway gas mileage?

I wouldn't trust those idiots at the dealerships to tell me how to turn on a light switch because they don't know anything about what they sell, only the mechanics know stuff worth listening to