Congrats on you first 5.0.
When I was 15 I had a rusty Volkswagen Dasher station wagon. So you are way ahead of me there. My first Mustang was 65 convertible that my dad paid $3600 for and it didn't run, need floors, doors, new interior, new top and a full paint job. I still have the car to this day, and it still isn't done

Keep in mind this was in 1989.
Just chip away at it and make sure you take your time and do it right. It will be a great learning experience and you will in the end be better for it. That and it will occupy your spare time and keep you from getting into trouble.
My parents found my extreme love for Mustangs when I was a teenager to be very annoying but later they were quite happy that I didn't get into trouble like several of my friend from the neighborhood.
Keep us updated on the progress and if it does turn out to have a whole bunch of hidden rust just yank the drivetrain out of it and plant it in a nice 2.3l coupe.