Rear end

[putnam00]

I bought a Eaton posi for my 3.25 rear end. I have a 700r4 transmission and so I I would like different gears. I thought I read when I bought it that the lowest gears I could put was a 3.42, but could I put 3.73s? I can currently go 100mph and I’m only pushing 2500 rpm, which is where my cam is just starting to be happy and I know if I can get lower gears I could get better fuel mileage. Currently getting 13.7mpg on the interstate at 80-85 mph. Or do you think 3.42 would be enough. I have a blueprint high performance 383 roller engine.