To replace the windshield frame, you'll need to find a rust free donor. If you become a subscribing member, you can post a wanted to buy thread. If you do a search, there are a few threads from board members who have documented how they replaced their windshield frame.
If you can't fabricate your own bumper/tire carrier, you'll either need to find a used one like lks dcvn has or find someone to fabricate one for you. Again, using the search function will give you some results of what other board members have done. BobbyK and Burt4x4 are the two that come to mind.
There is a place in Burbank called the GM Truck Center (
http://gmtruckcenter.com/) that "restores" GM trucks. One board member had his truck done there many years ago. It turned out nice, but I know he spent a lot of money there. I know there are a ton of other good shops in the SoCal area.