Others with more experience will be able to give you better advice than I, but I'm nearing the end of a long 544 restoration project, and I found that almost everything is available. Of course, mine's a '64. You don't say what year your potential new toy is, but it's my understanding that some parts for the earlier B16-engined cars are getting a little harder to find.

The only fasteners that I'm sure are NLA are the little metal clips for holding the skinny chrome strips on the dashboard. As far as I know all other fasteners are available.

The frames are really sturdy. The only places I had significant rust on mine were the bottoms of the doors and the very back of the trunk. I needed new floor pans in front as well, but they're cheap and easy.

My advice to you is to jump right in, but be forewarned that you'll probably triple what you think your budget is before the car is done. If you decide to take the plunge, you'll get loads of help here. I know I have!
--Ethan

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'64 PVMoneypit