Even in some of the Mecum auctions, similar vehicles can bring highly-variable results. One near the top of the chart as the other one is much more mediocre. In looking at the pictures online, the two cars looked more equal than the pricing might indicate. UNLESS there was something about one of them that killed the money. Or perhaps there was someone there that was the right person at the right time, so things happened well.
In many cases, the financial value of some vehicles does not reflect the ultimate utility of the vehicle. Which can make them fantastic bargains for somebody looking to buy one. Not so good for the seller, though.
Have you checked some of the online valuation websites? Hagerty, NADA, etc.?