We need to consider how OFTEN the truck is used. I bought a 1999 Ram 2500 V10 with camper pkg (dually springs), 100k miles, for around $3k US.
It gets 11 mpg, but has 3k lbs payload, and cost me barely anything in maintenance. I drive it 2000 miles a year at most, mostly in the bush while hauling a Bigfoot. Sits 9 months of the year. This is what the old big gassers are good for - occasional heavy hauling.
If you need the truck day in day out, or tow 10k+ lbs, then get a modern diesel or the 6.4Hemi/6.6 GM/7.3 Ford with 8/10 spd transmissions.