I know the fl60 isn't a hdt, but, it sure seems a lot heavier duty than a 1 ton Ford/Chev/Dodge p/u truck. I certainly see lots of them dragging around huge 5vers. I say leave the wheelbase alone. If you have any extra room on the deck you've got a nice place to store some bikes/scooters/lawn chairs/large tote with toys/etc....
'03 Freightliner FL112, 295" wheel base, with '03 United Specialties 26' living quarters, single screw, Cat C12 430 h/p 1650 torque, Eaton 10speed , 3.42 rear axle ratio