My 8.1 has the Ally and 3.73 gears, about 12mpg, with light loads.
It's more fun to drive than the LBZ, which weighs 10,000lbs with my bed, and gets about 18mpg.
Diesel here is running at least $.50 higher than gas, so by my math, it's cheaper to drive the gasser, although if I had my work bed...