If I recall correctly, Chapman used four cylinder short-blocks from English Fords, and Renaults, or Fiats, and fitted his own DOHC heads. Nifty little sports cars, along the lines of a Mazda Miata. The Seven was a more extreme creation, meant more for competition.
If you get a chance to sort through the "lumps", keep your eyes open for Weber 40DCOE carbs!