Fan clutch choice

For tight clearance, some people use a fan-clutch for a Jaguar. The one on my 1985 M-B 300D is also thin and has the same bolt pattern and water pump snout diameter, as I recall. But, even that was too thick for my 1965 Dart w/ 273 since I used the later aluminum water pump (1" thicker) so I could only fit a plastic flex fan. You should have more room to the radiator in a 1970.