I have a couple of internal memory expansion boards for the DEC
Pro-350. They have 128KB of memory (64Kbit chips). These work
in 350s and probably in 380s, too. You can desolder the 64Kbit
chips and put (sockets with) 256Kbit chips on them, solder in two
jumpers, and they become 512KB memory expansion boards (which work
for sure on the 380 and maybe on the 350).
(Note: This board does not plug into the expansion connectors,
but does plug directly in to the mother board.)
If you want one let me know. They're free, but if I get more
requests than I have boards, I'll give preference to anyone with
something to trade.
Dave