I think that the market has peaked. I don't think that you can go wrong with a numbers matching 70 or 71 (preferably a 71) but don't expect this car to pay for itself if you drive it at all. The insurance and upkeep cost will eat up any appreciation you have, not to mention the fact that in most states, you will be paying sales tax on the original sale (i.e. >5% on the cost of the car...$50,000 @ %5 is $2,500...ouch!). Now, I don't think that the priice will go down if you buy right (i.e. straight, original, documented and well-restored car), but there is a real chance you would end up losing if you buy a car where the body work goes bad in a year or two...ouch!
If you buy one of these cars, buy it because you like it....if you want to make money, go buy real-estate or invest in a well-managed mutal fund...I know, you can't drive a mutual fund.