I don’t believe that anyone is making panels for the big trucks. If you look close I think you will find that much of the parts from the pick up are usable for the big trucks. Use what is the same and trim the rest, these parts will usually get you close enough that the rest is easily filled in with hand formed sheet metal. Most all the cab parts are the same. Most of the differences in the fenders are at the rear and around the fender wells, those areas are usually fairly easy to form.
Give it a try if you lack the skill and or tools to form these more simple areas your self you probably shouldn’t be installing patch panels either.
If this makes you nervous just take a trip to a wreaking yard and see if you can talk them out of a couple wrinkled and rusted out fenders that you can practice on it doesn’t matter what they come from, they are just for practice. Get a couple books maybe a video or two read, watch and find out what tools you will need make a trip to Harbor Freight (you will not need the best) then when you are confident you can do the repairs on your truck. Oh and don’t throw them old fenders out you can use them in patching your truck if you look close you may even find areas formed just how you need them.
Good luck and most importantly have lots of fun.
