*MUST READ*--Flex Fan Danger--Be very careful working on old cars

That fan was so old and rusted ...it should have never been on the engine.

Glad you were ok in the end.
Always by fans that are rated for the RPM you'll run in and at the first sign of corrosion or rust on the rivets, replace.
A good Flex o lite fan is rated for around 12 to 14,000 RPM and will not come apart inside that range.