Agreed on mostly accurate numbering. It's about 9,000 made, give or take a few hundred.
As for 501 being an automatic, that doesn't require a frame swap. Read more about the 500 series here, and note the gaps, they are due to zero information being known: https://www.pjgrady.co.uk/500-series-chronology
The guys at Crawford are quite overprotective to the point of decay. If we can't get them to agree to let us fix it for free (I have tried too, not just DPI Josh), I can't fathom how they would be willing to let us put in a snake cam that they surely feel could destroy their "investment".
Although let's be serious, the value has tragically plummeted on account of it not running anymore. They dolly it around inside, it does not appear in their annual "run 'every' car in the inventory" warm-ups, not to mention they stopped showing it years ago. Crawford hosted a "stainless cars of history" display 3-4 years ago at the Autorama and 500 was a no-show. I have pics of this event I will dig out if anyone's interested. Almost a diversion, but likely the exact time when they realized how far gone it was. $20,000 for a historic beast would be seriously pushing it. And that's sad.