I'm going to go against the flow here and say that the standover height is just about right. Because of the characteristics of road touring, the bike should be an inch or so taller than a road bike. That being said and all other points being in good condition, I would work with the guy and see if he'll let you take it out for a decent ride. 20 miles should tell you whether it's a good fit; whether you're stretched out too much or bunched up. Take note of the shifting and the ride. All in all I wouldn't discount the cost of a bike simply based upon the age. My touring bikes are over 20 years old. The real point of the matter is does it do what it was intended to do when it was built and secondly will it do what you want it to do. It will stand or fail on it's own merit. $450 wouldn't make me shy away from the top of the line C'dale. After you take it for a ride, try working on $350 and settle on $400 if he's tough. (don't do it while you have a grin on your face from the ride high though)

Go here to find out about the serial number and look it up in the catalogue once you decypher the year:

www.vintagecannondale.com