[dsraven]

as you know, the original cabs, and aftermarket cabs, are all spot welded together, not fully welded at the seams.you could do the same thing instead of welding the whole seam and possibly distorting the flat panels. drill through the old spot welds and clean the metal up well, do any flattening needed etc to get a nice flat surface for the new panel to sit on. place the new sheet tightly against that, cleco or screw it down tight after the weld through primier. then do the spot welds one at a time and ensure they cool off well. good clean metal, shielding gas and a auto darkening helmet with the correct shade really help. do a weld. stop and cool it, do another weld, stop and cool etc. feel the panel with a bare hand and if you wouldn't put your tongue on it because it is too hot, then let it cool off before you do another weld.