Got one!
We have had our '78 for over 13 years, and she has been a daily driver for all of her time with us.
I firmly believe that if you let a vehicle sit, it will pine away and slowly die. With that said, I am leary of low mileage older cars without receipts to prove what has been done!
Page has started you out right, at the top of this page (in one tab or another) is a checklist for buying a vette. I suggest finding it, printing it out and reading it. It is VERY thorough!
I don't know of any 78 specific problems, just be aware that the 78s are almost 25 years old, and that is a lot of time...time sitting or time being taken care of. I'd certainly advise buying the BEST 'vette you can afford. When things go wrong on these babies, it's usually a pretty penny for repairs, unless you have a mechanic friend or can do most of the work yourself.
Good luck!
Heidi