Like the man said,- - - -get- - - -a- - - - -shroud! The V-8 models had the fan several inches behind the radiator because the engine was much shorter than the 6-cylinder. The distance was filled by a fan shroud that extended from the back of the radiator core to exactly halfway back on the fan. To work properly, the fan blade must enter the shroud only as far as the hub bolts, not all the way inside, and the shroud should be no more than 3/4" or so larger than the fan blade diameter. That allows the fan to pull all the air it possibly move through the radiator core, instead of pulling the air in from the sides.
Jerry