mercurymarauder.org is dead. I rarely see action there any more. I've been hoping to stir a little interest here. Maybe I can help.
You're going to want to check a '64 for rust in the rear quarters, rockers, and front fenders in that point right above the headlights.
Frames on '63-4 aren't nearly as prone to rust as the '65s, but take a look at it.
Take a good look at the fuel tank. It's different than the Ford and prone to rust.
Ford parts:
Doors are the same as a '63 Ford and are available.
Most drivetrain parts are easy to find.
If I can help any more, let me know. (Sorry for the delayed response)