cerb, I am going to dis-agree a little. You always have good info, so it is only going to be a little
As a tow vehicle, the early Dodge Diesel, 3. 07 gears and an auto was marginal at best. For start ability the 3. 07 was too high and too low for cruising (even empty) especially out here in the west with wide open freeways and 100 miles to anywhere. So I agree.
However, 3. 07 gears with a standard is very useable. 10,000 lbs is not heavy for this truck. All the 1/2 tons will pull this. If this truck were to be used as a commercial hauler I would say yes, go to a 3. 50 gear. 4. 10's with the little Getrag's short overdrive restricts your cruise speed and allows you to pull almost any hill in 5th. Not good, the 3. 50 or higher will force a down shift, good!
1st gear and 3. 07's will launch 10,000 lbs no problem. Once the truck is rolling, the gear choices make any rear axle ratio equal. He will be mostly forced out of 5th loaded so now the truck is kinda a 4spd. However as a daily driver this combo is great. I see in Robert's sig. he has two other trucks he can use for most of his towing needs. I think he is just playing with the 90

Nuf' ramblin I guess
Nick