Now I have an anorack but know nothing so does that make me a donkey jacket!! (Please note that the swear filter will not let me use A S S as in one word)
ADO 51 It was alleged to have been the Austin-Healey Mk3000IV prototype, hence the grill, which was custom made it was duplicated as a twin (ADO52) that became the MGC
In the now quite dim recesses of my mind (apart from the voices in my head) someting says the AH3000 Mk IV was a widened 3000 with a RR 4 litre as was in the VP Princess. The RR 4 litre was a light alloy engine not that much heavier than the original 3 litre Austin and having a 6" wider track it handled and cornered quite well. The added power was also nice. Far better that the MGC ended up with. Unfortunately they couldn't get it into production as BMC was merging with Jaguar by that time and it would have been a competitor.
Have to fly now as I have Bowels - sorry bowls to go to. Will leave for others to flesh out as I cannot research any longer.