like some thoughts on 2 speed rear axles

[AHuggard]

I very just bought a pretty much stock 93 D250 TD one owner. Has a 3.5 rear end and standard duty automatic with under bed cooler. No engine mods but I have already installed a second battery, tranny temp gage, and a tach. Still haven't got factory manual yet. I am already well advised that the tranny is the weak link; however, the local Dodge service mamager says they have replaced the rear end 3 times in this truck. I know the prior owner and he pulled a 23ft 5th wheel camper OTR. Now, not wanting to replace the tranny, cost and I am old so I like the auto shift, and wishing to use the trucK for kicking around as well as work, it seems to me that a 2 speed rear end might be helpful. Say around 4:11 for pulling and the 3:5 ratio for normal. I am not sugesting that I would try to split shift just leave it in high or low depending on what I am doing. I am not an over the road type but I do live in the hilly part of the Kansas country. (Yes there are hills in Kansas) I could be way off base with this thought but who knows maybe one of you great and wise adventurers has done it or at least already thought about it. As with most folks wealth seems to have eluded me so the availability of remanufactured or quality used sources would be helpful in this discussion. Any one want to comment. (Your stupid! is an acceptable answer as appropriate)
Al, I love the truck, Huggard