HevyHauler,
If you want to swap Medium Duty Fenders for Heavy Duty Fenders you need to use all of the outer sheet metal on the front clip. The Heavy Duty truck Fenders, Upper Grille and Lower Grille are all different than what the Mediun Duty trucks have. Inner fenders and core support are the same. It would be lots easier to just swap complete front clips. The only negitive I can think of is the HD fenders might hang lower on the Med Duty trucks due to the shorter frame rail height. The front frame horns might also need to be modified...the HD frame horns have a deeper offset.
Mike B
