Dart Swinger I found today - should I buy it?

Factory (pumpkin orange?) paint and white vinyl top, virtually rust free, factory 318 A/C car (blows warm but all the parts are there), has an aluminum intake and 4 barrel, dual exhaust, seems to be stock otherwise. Interior looks near-new (I think the front bench seat has been recovered in original-style upholstery), perfect headliner, small crack in corner of dash pad. Not so much as a parking lot ding anywhere on it!

Only problem is that the engine has a vibration. Oil pressure is good, no smoke, runs well - I'm guessing it has had some work done and has a converter-flexplate mismatch / balance problem.

What's it worth?

http://i75.photobucket.com/albums/i301/300x500/IMAG0001.jpg