You're right, don't spread beyond the 128mm. Are you sure the Sachs is not an 8 speed? I know, hard thing to overlook, but I've done it in the past!

So, if I understand correctly, the Regina was set-up to work with 128mm OLD? Now the wider Sachs require more room, but your wide locknuts don't allow the hub to move any further left? Those nuts are standard issue on all those old Campy hubs, BTW. Ditching the Sachs for a narrower 7 speed freewheel might be the most sensible thing to do.