Thanks everyone for the responses. My truck is originally 2wd but I was able to pick up all the 4wd parts for $350 from a guy who was upside down in a burn vehicle he bought for his own truck. I intended to fine a 4wd zf6 but as stated before couldn't anywhere.
This is a huge project that is starting soon. Haven't done a build in a very long time so I'm pretty pumped over this. Going to be rebuilding the LB7, rebuilding the ZF, rebuilding the X case, tearing the truck down to the frame. Stretching and coating the frame, switching to a crew cab body that I am doing inside and out. Cut the firewall to be able to push the entire driveline back 2" for better weight distribution and to provide easier valve cover removal. Will definitely be posting lots of pictures once it starts.
Before anyone starts in on me about why not just buy a 4wd or buy a newer truck, I just don't want to. I bought this truck for $2000 and so far I am into it for about $3500 including the price of the truck. When this is finished the final cost of the truck will be between $20 to $23,000 and it will be exactly how I want it, practically brand new, better than the factory could build it and own it free and clear. To me that beats the hell out of paying and partially financing $30,000 for a newer duramax that gets less mileage, has to comply with emissions, nothing would be new or exactly as I want it and worst of all, missing out on the thrill/late nights of a build and being able to tell people "I built it ". Dont get me wrong, the newer trucks are great but I enjoy the build. I turn wrenches for a living and it's my passion.