I wonder - could these be rebarrelled with a barrel stamped '7.65 mm Browning?' That would take 32acp brass, bullets and dies as-is because 7.65mm is the euro designation for the 32 ACP; which is, of course, not *actually* a '32 caliber' at all (just like the 38 special is actually closer to a 36 caliber than a 38, for example)
There was a court verdict saying that 7.65 Browning is still a 32 cal, and it's a precedent and has not been reversed.
That means that even a longer bbl in that calibre is still a prohib. Too bad. NFA should have the info as IIRC they were closely involved with the case.