A clutch fan is better than a flex fan, but don't know if one would fit a slant. The engine is longer than a V-8, so less room to the radiator. Maybe Volare or Aspens used them. I can't fit even a regular factory fixed fan in my slant since the p.o. put in a non-Mopar radiator. It hasd a pusher electric fan (M-B) and no mechanical fan. I could fit a thin Summit nylon fan. A small mechanical fan, plus an electric should work fine and be efficient.
Besides the Jaguar clutch fan mentioned, perhaps one from a M-B like an 82-85 300D would fit. Euro clutch-fans are much narrower. I tested a Mopar clutch on my 300D and it fit the water pump, using a bushing that came in the box, so a 300D clutch fits a Mopar water pump if you drill the center hole bigger (small block, probably same for a slant).
