Well it seems it is an AC- Bristol single seater from 1959. Must admit I have never heard of it, nor have I ever seen a period picture.
You won't have seen a period picture, because it's relatively new. I asked what it was, and you answered so the point is awarded.
The car is discussed on another well-known website. AC-Bristol AEX748 was crashed by its French owner, and parts were used to repair another AC BEX682. The other parts were made by Bernard Maitre into a monoposto and raced in France. Any remaining pieces (like what I hear you all cry?) were used by Nick Upton to build this car. I have no idea which car used the engine but we all know how modern historic racing works - maybe it's got the rev-counter from the AC-Bristol.
The end result seems to be 3 cars out of 2 identities.