The long spacer and out of balance fan blade metal fatigued the snout.
NO NEED of a spacer that long. My dart 273 2bbl runs fine all day long with the stock spacer and stock 7 blade fan, no shroud as it came from the factory.
As for early Cast iron or later Aluminum water pump. they are different in many ways.
- the inlet is on the wrong side
- the mounting bosses are not the same height for the alt etc.
- the overall length is longer so the fan belts will not line up correctly
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