Need some help with getting ready for pulling heavy loads

UPDATE, ran the first load at 86,000 gross last week, and it wasn't too bad. Mileage sucked big time (4.81, and I usually get at least low sixes), but I had some time pressure to get it done and the foot was definitely on the floor a lot of the time.

There were many times, however, I would have loved to be able to split the top gear. The next truck is definitely going to have a few more gears, I think it will save me quite a bit of time both uphill and downhill.