This was the subject of at least a couple of decent magazine articles over the years. It was initially rebuilt by Bob Gardner (who also restored the convertible) back in the late '80s/early '90s.
IIRC: After it's rally career it was later used by Rover as a prototype 2200 and it was in this state when Bob bought it, though extremely rotten. Bob decided to rebuild it to it's original rally car guise and stored all the 2.2 bits (wonder where they went?) He reshelled the car with an ex-USA 1965 car and transferred all the reinforcements and such across and scoured the land for other rally spec bits.
So it's genuine, but it's not. If you get my drift...