[Tishabet]

Hey guys,
I have a friend (no, really) who came to me with a quuestion about his dad's 67 impala because he knows I restore antique cars. Unfortunately, I restore cars like my current project, a 1938 Buick, not muscly american cars from the 60's, so I couldn't really help him aside from pointing him to hemmings. But I figured I would ask here since there seems to be quite some automotive expertise present
The car is a 67 impala convertible which has been in dry storage since 1974. The owner (my friend's dad, the original owner) mothballed it by supporting it from jacking points on the frame and putting oil in the cylinders after running the gas tank dry. The engine hasn't been started since 1974. The mileage on the car is in the mid 60s. The engine and body are spotless with the exception of the hood, where someone placed a can of paint thinner which stripped a circle down to bare, clean metal. The body color is baby blue, engine type is unknown.
This is all hearsay from said friend, so I'm a little skeptical about the "immaculate" body, but in any case he's not trying to sell it to me, he's trying to figure out fair market value because his dad is tired of seeing it sitting in his garage.
Any guesstimates/advice/etc?
Thanks!