So, coming back to seeing what opinions have been expressed on this subject after some time, apparently the GT40 owner's world accepts the ex-Salt Walther car as original today though it has had a chassis change/update/replacement. I wondered about that until I got a new book on the Lola T70 and found chassis replacements much more common in that model of race car. I guess I am used to the Ferrari world where chassis changes on the pre-'70 tube-framed cars are very rare.