You would want all the bolts that hold the fenders and front sheet metal loose. That includes the inner fender to cab bracket points, the braces may hinder it too, and the radiator support to the frame. They don't really enlongate the holes for a bunch of adjustment, but you may be able to tug enough at the front, especially if you don't have the grill in or radiator then you could use a board across the radiator support, and chain or rope and a comealong to hold some tension while you tighten the bolts you mentionen. That is if you need that much forward movement.
If they are repop fenders you may have to rework the mounting holes to allow the adjustment.
