A shroud makes all the air the fan moves go through the radiator, instead of some of it bypassing the radiator core and not contributing to the cooling effect. Any good sheet metal or air conditioning shop should be able to fabricate a rectangular box the size of the radiator with a hole in it slightly larger than the diameter of the fan. Bracket it to the radiator mount so there are no big leaks. Important- - - - -don't fully enclose the fan. Half the fan blade depth should be enclosed by the shroud, not the entire fan, so position the shroud so the opening is even with the front of the water pump flange.
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!