If the fan blades are within an inch or so from the radiator core, a shroud won't make much of a difference. If you choose to use one, be sure it only covers half the depth of the fan blade. Totally enclosing the fan will reduce the volume of air it can flow pretty significantly.
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!