It really is all about how much you want to put into it. The cab to my 79 is one that most would have sent to the scrap heap, I have/have to patch things everywhere and a lot in the places that nobody makes patches for, like the firewall. For me however I would rather fix the rusty cab and save having another square being decommissioned and its cab taken for another truck. This cab is the cab that the truck was born with, if I put a cab from an 83 on it would it really be a 79 anymore? To me it wouldn't be. Its history of being a sheet metal company's work truck and its abandonment behind a machine shop for over two decades would be lost with a different cab. To others that just want a truck and don't care the history of it, that might be just fine, I personally like knowing the history of it and trying to keep that history. You could get screwed too with a replacement cab if it had previous body work done to it that might be hiding lots of ugly stuff underneath, putting you back to square one.