Todd, I am very interested in getting more details to support your assertion!
It is often difficult to authenticate a rally car- genuine factory prepared cars were built as spares or to pre-run major rallies, and license plates were changed back and forward between competition cars as proved convenient for the mechanics, and then there is the problem of replicas.
I once wrote an article on the history of the three
TR4s which were used in the 1964 Shell 4000 Rally in Canada, so I am aware of the problems of tracing the history of a competition car. (This problem is particularly difficult on a car with a separate chassis, where the same body may be used with a different chassis!)
In addition to rebuilding or re-shelling after major crashes there is continuous development so that even after a single season several mechanical details on the same car may depart from the specification at the start of the year. Not even the drivers can be certain of the identity of cars they drove- and I have found myself that John Buffum does not reply to unsolicited emails from strangers- probably wise. This license plate was on the car(s) driven by Buffum in the RAC rallies of 1980 and 1981, though that may mean nothing.
I think the generally accepted authorities on these cars are Bert Smeets in Belgium, and of course Graham Robson and Bill Price, who have authored books on them. I would be interested to know if your "good authority" is one of these three, and also what evidence supports this assertion. Please give us more details!