About That '64
By coincidence, I'm the happy :L owner of a '64 roadster with 103K on the clock. Even with that low mileage (2.7K miles/yr average over 38 years) the last two sets of tires removed from the car had died of old age, with lots of rubber on the tread. (Both sets had one tire expire in spectacular fashion, despite being carefully inflated, etc. One threw a thread, the other blew a hole out the sidewall!) In the early years, this 'vette was my daily driver and thus had 57K in ten years, still not a lot. Then it was in storage for three years while I was overseas, and since has been getting ever-decreasing mileage, especially ever since '97 when we bought the '98 roadster sitting alongside it in the garage!
The car has original paint, original engine, even the original soft top which isn't all that bad except for the discolored window. The springs sagged (but then, I did too) and the carpeting and seat covers have been replaced. About everything else is original except things like waterpump (twice) and "consumables" like battery, tires, windshield wipers, etc.
Even the original owner: the reason I'm so sure of all this history is that the proud owner has been ME since Dec 9 1963. (Paid $4,050 with a discount!) Since I know everything that's happened to the car in 38 years, I don't have any problem believing that mileage, but a lot of people do.
On the car you mention, the 250 hp 327 was the "base" engine that year. (Mine was one notch up at 300 hp with the Carter 4bl carb.) The 47K car that you mention has likely passed through many hands (you didn't mention anything about limited ownership) and would have had to AVERAGE only a hundred miles a MONTH for 38 years. To me the owner would have an uphill battle proving it's been driven that little.
Save the wave!
Fred