Hi, and welcome to the forum. I am doing a frame-off to an 80. I found most of my "hard to find stuff" on Ebay. A complete 79 is being parted out now. Ebay auct# 130096160010. I recently saw doors and quarters for sale too. I'm not sure if the auctions are still active, but I can check with the seller of the quarters if you like. I had my headliner material replaced for $80.00 at a local interior shop. As for the 80 front end, it will easily fit. The hardest part of that swap will be the wiring. Get the harness with the clip, if you don't already have it. Also, check out the small block section of this forum before you decide to change to a Chevy engine. After all, you didn'y buy a Monte.
Best of luck with your project. Jim.