[LMH]

SAAC isn't silent on the subject, the entire registry is proof of it. It has established some working definitions which are:
Original: Main frame tubes and pieces carrying the serial number stampings have not been replaced or altered and were produced between 1962 and 1968.
Original/Restored: A car having less than 50% of it's original substructure or bodywork replaced but not the main frame tubes or pieces carrying the still existing serial number stampings.
Original/Rebodied: A car having more than 50% of it's original substructure or bodywork replaced but not the main frame tubes or pieces carrying the still existing serial number stampings.
Reconstruction: A car that has been rebuilt substantially to original specs, even replacement of main frame tubes but where some part of the car existed prior to reconstruction. Traceable documentation must be present.
Air Car: A car built from scratch, no original or legit documentation or serial numbers.

Now it might not be above some owners to misrepresent their cars as something they aren't for obvious reasons ($) but the registry exists to keep track of each car.
Larry