you want to stop looking at duallies for D60's.you'll have much better luck searching the SRW trucks (4wd's only.)
9 times out of 10,if the truck is not listed as 4wd in ads,then its not.they are worth more than 2wds,and thus the importance of listing that info in the ad,when asking more $ to its comparable 2wd truck.
look for the axle and hubs in pics.
your TTB no good?
generally the reason people want to switch to the D60's with f250's is for working the front end(plows etc) or lifting the truck,hard off roading etc.
if your TTB just goes along for the ride,and is simply used for more traction (4wd use) then it's pointless to put in the stiffer riding d60.
just because people say they are better,doesn't mean everyone actually has a use for one.
you should plan out the mod carefully,because if you don't off road/lifts,large tires,mudding,plow,etc.it could be a large waste of $.
TTB's don't eat tires either for the record (if simply used just for traction,4wd/street use.)
people neglecting to maintain the front end and keep them properly aligned will eat tires though.
years of first hand experience.