The Fixes are ugly, but might be good enough to be operational anyway if just a partially blanked EPROM.
That might certainly cause a grey screen, if the EPROM code doesn't ever finish executing. New copy of Mach 1.31 or Magnum or whatever might just fire the thing up.
Full upgrade to an 060 might be tempting, they do run a lot cooler and faster. Maybe long term. Phone Amikit, they're in the UK, they might be able to sort you something suitable sir.