The problem is that even though is is clearly the "Kosoff" vehicle, to believe it is ALSO the very same one that transported JFK would require that:
1. At one point, a previous owner (Kosoff, Jensen, or perhaps someone in between) started claiming that it was the historically significant vehicle even when no such claim had ever previously been made, even when the it was offered for sale as late as 2009 for $41,000. Jensen did say in the B-J press conference held just before the auciton that at the time he bought it, it WAS claimed to be one that carrried JFK.
2. "Proof" (in the form of the Hogan-Shields letters) that it was said vehicle came to light in late 2010, and has now been discredited (and the data plate's authenticity called into question as well), but that still does not prove it WASN'T the car.
Assuming Jensen was duped, then the Navy data plate had to have been on the car BEFORE he bought it. Since it showed the same numbers that appeared on the door of the vehicle in the Andrews AFB footage from the night of the assassination, he undertook an "exhaustive" search to prove it was legitimate. Said search did not include following up on ANY lead, even one that might disprove the claim, since he was clearly told in August 2010 (after showing the car at a convention for military vehicles) that the real ambulance was destroyed and he immediately rejected such information out of hand (see professionalcar.org thread).
Happily for him, the search for proof was ultimatley successful in "the fall of 2010" (as stated by Jensen in the B-J press conference), just in time to offer the vehicle at the Scottsdale auction. As for where this proof came from, in the words of B-J's Steve Davis at the same press conference...."who knows".
