1968 Bonneville convertible. Whats it worth
 

I have a lead on a very nice 68 Bonneville convertible. It is advertised as having a 428 and a 4 speed tranny. Going to an an auction where it will be sold soon and am very interested. My question to you guys is. Assuming under 100k miles, in above average condition, what would be a good price to buy this car at. I specialize in 60s cadillacs and have never owned a Pontiac. Love this car but want to make sure if I purchase it I buy it right. I know it is hard to estimate without actually seeing and driving the car but any help would be appreciated. Here is a link to the only picture I have of the car http://s250.photobucket.com/user/ben...0x450.jpg.html. Thanks