I have a 62 one ton panel that weighs in at 5800 lbs before bondo , a warn out 235 with a t5 with .73 o/ d and a 4.57 rear end with 30 in tires. I run the truck between 2500 rpm and 3000 and seems to be the perfect set up for Me right now. I did have a 3.90 rear end in it which dropped the rpm to the point where it wouldn't climb even a gentle grade at high way speeds with out dropping a gear so I put back the 4.57. This not only improved drivability but improved my mpg as well.
At one point a few years back I lost over drive and drove home ,a 600 mile one day trip at 60 mph and 3000 rpm for about 12 hrs that was with the 3.90 rear end,.and the truck seemed to have been running at its best on that trip. I learned on that trip that rpms are your friend.
Once I repaired the o/d I went back to the 4.57 rear as I like to travel at the 70-75 mph on the longer trips of which I do many .
I don't think over gearing it is the answer.
I had 5 different ratios for the rear end here and the 4.57 is the one that worked best with an o/d trans. There is only a couple of mph difference in high way speed between a 4.10 and a 3.90.
John
