My local guy gets his stuff from DAR, but I buy from raybuck automotive, from what I've seen they were the cheapest, bought 2 door skins, rocker skins, cab corners, and upper wheel arches from them.
73-87chevytrucks has some stuff, not sure if it's cheaper or not though. I now I saw a 5 piece cab repair kit on ebay, and capt. kaos on 73-87 was the same price.
I also second welding, I tried panel bonding BS and it sucked, would not hold anything, ended up cracking around the edges, and had to put rivets in to hold the pieces, and it still cracked. So sometime soon the 84's bed is gonna get stripped, upper arches welded in place and repainted.