There may be more to this than just moving some wires around.
Accuphase is a small volume producer that makes units by hand in small batches to order spec’d for specific markets (ie voltages etc).
Are the input amplifiers the same or different for different markets? What about the power transformers?
The resale value of a modified unit will be greatly diminished by those modifications. Even though the 100v units are much cheaper, it may end up being an expensive mistake to try to convert one to 120v. You certainly won’t get any help or information from Accuphase.
Buy used, or buy something made in your own country - or for your market.