Rear end ratio ?

[farmer70]

Rear end ratio 13 speed 3.21 rear ends with 11R 24.5 rubber. ISX 2350 500 hp. I usually run in 12th with the cruise set on 65 this puts me right around 1500 rpm. I thought it would be Ok but I don’t really like the tall ratios. What would you guys recommend I go to if I changed the rear ends? 3.42 3.55 3.73 ? I generally operate on two lane roads and a little bit OTR. On flatland in the plains usually about a 350mile radius of Garden City KS. Loaded 80,000 lbs looking to go maybe 90,000 Lbs. Appreciate your advice.