The end all to valuations is what a willing buyer and a willing seller can agree on. A good marketplace for antique cars is www.hemmingsmotornews.com (or close to that) and they reach a world market.
It will matter where the car is, any rare options, L or R hand drive and the actual mileage or Km on the vehicle. Also is it original or a restoration. Originals fetch better money.
If you want I'll move this thread to antique car talk - just ask or another may do that,
T