My suggestion would be to have the owner (assuming it is a private owner) take the car to Crawford's Z Car Service in Nashville and have them look it over. They have been servicing Z Cars, Datsuns, Nissans & Infinitis (and building and racing Z Cars) for over 30 years. They know their stuff. Many 350Z owners on the 350Z board know of Doug (the owner) and Crawford's as they built custom aftermarket parts for the 350Z (particularly the Crawford Intake Plenum).
I would be happy to meet them down there to look over the car and give you my opinion as well if you wanted, though Doug and his crew would offer expert opinion.
Crawford's:
Crawford Z Car Service:: Nashville TN - Nissan & Infiniti Repair Specialists