Based on what you are saying - you are going to need a donor cab.
Being in Indiana isn't going to provide you with a bunch of these sitting around in decent shape to get solid sheet metal from.
I see you already found this one -
http://67-72chevytrucks.com/vboard/s...d.php?t=734066
If you don't see one on here that is solid - you can start checking local on CL:
https://indianapolis.craigslist.org/cto/6051735257.html
https://cincinnati.craigslist.org/for/6069730090.html
WTF? -
https://louisville.craigslist.org/pts/6031331878.html
https://cincinnati.craigslist.org/pts/6064067267.html
https://bloomington.craigslist.org/cto/6059245763.html
https://louisville.craigslist.org/cto/6052981534.html
^ - No connection to any of these - just did a quick search near Indy.
Depending on the condition of the rest of the cab - it may be worth it to check out a solid replacement cab to save you time/cost of fixing a few parts of your current cab.
Good luck in your search!