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

Hello Dennis Jackson,
Welcome to FABO.
If the "Rust holes in a lot of places on the chassis" are not of a safety concern and OR if they are and you can repair them so the car will be road worthy and safe then it looks like a great project car.
Keep in mind that when doing frame repair it can get difficult to work on without a lift, flat surface (jig plate) and or an rotisserie as examples.
Also being that its a convertible the body should be supported (X bracing) to keep it from twisting if you need to replace some of the underside parts (unibody frame rails). There are lots of YouTube on this subject.
Look it over real good and then decide.
Overall it looks like the car is mostly there and sounds like you have the majority of donor parts included with it.
From what we can see it don't look its in that bad condition (Most of us here have brought worse cases back to life)
As Toolmanmike stated some parts are one year only and could be a PITA to find.
Good luck and your fellow FABO members are here to help with questions and conserns you may have along the way.
Keep us updated.
Stay Safe......
Happy Mopar :)
Arron.