So I may have figured out why the PO put this up for sale: the trans crunches going from 1st to 2nd (137,000 miles). Now I have in the past had sports cars with this issue and learned to shift them just so, such that I beat the crunch.

The trans on my Miata tends to crunch less or not at all after warming up.

Possibly I should try some magical mystery oil?

Under the car for the first time today (at the mechanic's lift) and confirmed PO's claim of no rust, yes! and the boots on the CVs are good. Yes to that too. And that the exhaust is new and stainless steel, very good.