To repair rust on a Ford truck with a replacement panel, determine which panel is needed, as well as the year and model of the truck, and procure the replacement panel. Remove the rusted panel, and install the replacement to eliminate the rust.
Once the new panel is obtained, determine if it needs to be trimmed in order to fit. Ideally, only the rusted area should be replaced in an effort to keep as much of the original body as possible. Use metal shears to cut out the rusty portion of the panel, and trim, hammer or bend the new panel in order to fit it into place.
Tack weld the new panel to secure its placement. Alternate between spots while welding to avoid heating one part of the metal for too long. When the panel is completely secure, use an angle grinder to grind the welds until they are flush with the panel's surface. Use a seam sealer to reinforce the seam, and then prime and paint the panel to match the vehicle's original color.
Historically, auto body replacement panels have been obtained by visiting junkyards or vehicle salvage yards and removing them from vehicles with a similar make and model. As of 2015, stores that concentrate on auto body repair have brand new replacement panels available for a variety of vehicles. Ford truck panels are available for models produced as early as the 1970s.