$27K is not bad for a complete clean car.
Just for comparison, I have well over $30K in my 69 and nothing to show for it yet. It is an investment, just not in the traditional ways. The return on investment is the fact that you will have tons of fun and meet many new and interesting people. When you invite friends and family over, many of the conversations will end up taking place out in the garage, and the visit won't be complete until everybody has gone for a ride.
When you are cruising down the road in a sexy sleek and powerful piece of history, all eyes will be on you. Drop the top, and hang on, because the roar of raw untamed power, fuel burning rich, and tires squeeling will make you feel like a kid again.
A Z06 could cruise right by and nobody would notice compared to that wicked rag top shark.
So, if you can afford it, and it is not rusted out underneath, then buy it. The good news is, while you may not "make" money off it, chances are you will at least be able to resale it later at or near the current price. You can't say that for a new car, even if you buy it at invoice.
Please post some pics when you bring one home.
All I can really suggest is you get a real close look at the frame from underneath, especially just in front of the rear tires, the radiator core support, and the windshield frame. If it is a "frame off restoration, demand to see photos of the process and feel free to share them our way and we can tell you if it was really frame off restored, or just got a fresh coat of paint.