Looking for a 409 engine bonnet-compatibility?

[Kevin H]

Before cutting a bonnet to create louvres I would suggest improving the engine cooling system. The original configuration of electric fans (or a single fan on the 409) mounted six inches in front the radiator, albeit in a cowling, seems inefficient by modern standards.

I would suggest replacing the original radiator with a thicker, higher performance radiator and mounting modern fan or fans directly onto the front AND rear of the radiator - with the rear fans designed to pull rather than push air. This will both improve engine cooling and get more air flowing through the engine bay. Obviously removing the original cowling and fan (or twin fans on the later V8s).