CREATE TABLE table_51573 ("Season" TEXT, "Champion" TEXT, "Team" TEXT, "Chassis" TEXT, "Engine" TEXT)

Who was the champion that drove the car with the Ford engine in 1971?
SELECT "Champion" FROM table_51573 WHERE "Engine" = 'ford' AND "Season" = '1971'
SELECT "Champion" FROM "table_51573" WHERE "Engine" = 'ford' AND "Season" = '1971'