Actually a good point to consider is wher you are located. ie.U.S., Canada, UK,Aussie-stralia or elsewhere.
As the saying goes in real-estate; location, location, location
Even in the U.S. cars can vary in desirability by locatation. For instance an older car from CA ro AZ vs. a rustbelt car MN - CHI - NYC - MA Presumably a car from the inner city in the rust belt will be a well salted (and potentially rusted) worn out pot-hole pounder vs. suburban driven and concievable garaged (presumable with better cared) CA car, right? Exepting of course flood damage, eathquake damage, hail, drive-bys and other acts of God .
Location will affect the condition of the car or at least perceived value (some people refuse to by any cars from any central city based on that sort of pre-judice).
Rather than rely on a 'book value I would do some historical price tracking of your particular model in you region. Being that it is a drive-able classic, you may get a better picture that way rather than using a Kelly book that artificially inflates or undervalues cars based on national averages.
Unfortunately eBay will other car sites will not be much use as they or only showing current vehicles, so a quick trip to the library and look through some old newspapers may be in order.
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