Congrats on your project. My first car was a P15 and I still have it. I just got it back on the road after 30 years in a barn.
These things come apart much easier than they go back together. In a weekend, I blew it pretty apart and it sat for over 3 years in pieces because it was a bit overwhelming once I was staring at a pile of parts. It really wasn't a car at that point. As others are saying, resist the temptation to turn a manageable project into a massive project.
What I finally decided to do was go with the Roadkill philosophy and just get it running, and only fix structural rust and then figure out what I really want to do with it and then work on that part. Don't care what car looks like, just get it on the road.
As soon as I got it running, it was a car again instead of a pile of parts. It motivates you. Now I drive it around with a piece of cardboard covering the master cylinder hole, zip ties to hold open the vent window and I work on smaller projects of a running car. I have the parts to fix both, but neither stop me from going to the parts store in it. One day I may even paint it. :)