This is the Farrallac Mk2 - the original car was destroyed in a major accident. The front end is fashioned from a Maserati nose, and the rear from an Allard J2. Power is from a 6-litre Cadillac engine, hence the name of the car. And here's a photo of the young Peter Collins and his original car. (To be pedantic, the original car was destroyed in 1959, and this puzzle car first competed in 1960.)