The wedge-shaped, gas turbine-powered Lotus 56, one of the most unusual cars ever to race in F1, was originally designed to compete in the 1968 Indianapolis 500 where it nearly won, but with USAC introducing a ban on gas turbines and four-wheel drive for the 1970 race, a new B variant of the car was built to Formula 1 spec with an eye to replacing the failed 63.