I've had both a "95 with the 6.5 way under powered for pulling would get 16-18mpg not a dually. The '97 with 454 would pull my 32' enclosed no problem about 10mpg everyday abouy 6mpg towing. If you buy it and put the 454 in it you are going to have to get the right computer,change transmission and possibly fuel tank not sure but i'm sure the fuel pumps in the tank are different. Just something to think about.