95 5.9 ram 3.55 to 4.10 actually picked up 2-3mpg in most driving, the OD + lockup was too lazy

My Fury 383 commando spec with 727/3.23 and then a500/3.91 the mileage is actually a little worse with the OD because I don't drive fast enough. The 3.23's were no fun @ 80mph commuting but I don't spend enough time at that speed. The 727/3.23's were better at 60-65mph. With a bigger cam I think it'd make even more pronounced difference as you lug the slobbery cam.