Ken,
All the old Grand Records ('72-'76) I ever saw had bottom brackets threaded Swiss. However, if yours has right hand threading on the drive side, perhaps someone re-tapped it for Italian on one side only? I have seen this done a few times over the past 30 years (but usually from French to Italian).
What (size) cup is threading into the R/H side so you know the threading is "right hand"?
Chuck Brooks
Malta, NY