Considering a '67 Dart GT Convertible as my first project. Am I insane?

Welcome. Great car and as you stated yourself it needs more inspection. I feel $7k is too high given the amount of cancer, but a 4 speed vert isn't that common. As stated there are some 67 only parts then there are convertible only parts. So not the easiest for a beginner. How much are you willing to do your self? What is your goal and what is the budget? Are you looking to stay stock or going all out performance or somewhere in between?
Thanks. Good to know on the uniqueness of the parts. Not sure how much of the '69 donor car will be usable then. I will do as much of the work as I'm able to do. I'm excellent at mechanics, pretty good with body work and will get better as I go, totally new to metal work, but have watched a lot of "Iron Resurrection" and "Garage Squad" and the like (so I'm an expert lol). The goal is somewhere in between. Probably in the 'resto-mod' category, with mostly stock looks and weekend driver type performance and drive-ability. I've got plenty of time and will pace myself on the budget, but recognize I will probably always have more into it than it will ever be worth.