1996/99 dodge cummins swaps

ECM different for manual and auto trucks, driveshaft lengths different, brake system will be different due to the 99 will have rear discs, why dont you get the mudd truck out and clean it up and get it running and part it out for money enuff to have the gear ratios put in by 4x4 shop you want, that 6 speed will bring more than enuff money to pay for that, all depends if it has had water damage inside everything for years, bearing rusts, rats eat up wireing, if you have to ask how hard it is its not for you I figure unless you have a 2 car shop and can put both of them side by side and transplant back and forth and have $2000 cash for misc parts, you could get lucky or wrecked, all depends on condition of the truck, are you sure they did not blow it up and leave it there on purpose, usually nobody leaves a cummins 4x4 anywhere even if a insurance claiim and written off, pull it out, get it running, part it out and buy what you want new with the cash, 6 speed 1500$k $1500 motor, diffs$500 each transfercase$500 $3500 cash would get all new lower gears in the dually and discbrake conversion and maybe new injectors and a smarty controller or edge and a 5 inch exhaust and you still have a stock truck dually basically without all of the ecm and wiring changining out etc etc, i would not fool with a transmision been sitting in mud for anything especially if you convert from auto and find out its worn out in the first place, how many miles on the mudd truck??