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

Since you are not Gas Monkey Garage and not going to send it out to the blaster (just to get back half of what you sent) get under it with a screw driver and hammer, and see how bad things are, as in subframe, rockers anything you doubt.
If you have all the odd 67 parts AND vert parts that is huge plus.
Hint: any car from Mi. and any vert scares me (and I'm fearless!) LOL . No really just remember, any car can be restored, some just take more work and more $$ as in $$$$$$$$$$$$$$$$$$$$$$$$$ sometimes!!! Good luck!