If the position of the fan blade ends up more than a couple of inches from the radiator core, it would be a good idea to fabricate a shroud that covers half the depth of the fan blades. That's the ideal position for the most efficient air flow, where the opening in the shroud is even with the midpoint of the blades. Fully enclosing the fan actually results in less airflow than letting half the blade be exposed.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!