Ok, so to get more air flow through the radiator you'll need to manage the air flow better.
The first thing I'll suggest is you need to seal the heat exchanger area up so the air must travel through the exchangers and not around them. This is easily done with 1/8" thick fiber reinforced rubber sheets. You can attach them to the walls of the compartment in front of the exchangers and allow them to go as far back as the coolers making a gentle fold onto the edges or the face of the rear-most cooler.
The second thing is a fan shroud. If you don't have one, you need one. If it's a 7.3 Powerstroke radiator from a super duty, get a fan shroud for a 99-03 7.3 truck or van. You'll want to size the fan to make best use of the shroud of vice-versa, or build a shroud to work with your existing fab. I don't think you can get electric fans large enough for your needs.
Third, exterior aerodynamics. Back in 1987, Ford sealed the upper grille opening on the Mustang GT. Looked cool but created an airflow problem. So the engineers and aerodynamicists figured out that a 3" plastic air dam the width of the radiator forced enough air up into the bumper cover and then through the radiator to cool the cars sufficiently. Placing the air dam directly under the radiator served two purposes though. The first was forcing air up into the bumper, the second was that it creates a low pressure area on the engine compartment behind the radiator, and this is the actual reason the cars ran sufficiently cool. Take that ugly piece of plastic off and prepare to overheat those cars.
Airflow is your next mod.
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The Current Truck (Oct-2013 to Present):
1999 (Early) F-350 Lariat, CCLB, SRW, Black/Tan
7.3L Powerstroke, 4R100, 4x4, 3.73, 37x13.50-18s, '05 Axle Swap, 6" Fabtech lift, GTP38 "D66" turbo upgrade, SCT 4-position chip with custom tuning by me, Straight Piped 4" down pipe through 5" dual stacks, N-Fab full length triple steps, Pro-Tech cab guard and tool box, louvered 5th wheel gate, Hella 500 Fog and Driving lamps, much more to come...
The one I'll miss, (Mar-2009 to Jan-2014):
2000 Excursion XLT 4x4
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2005 F-350 XLT, CCLB, SRW, 4x4 FX4
6.0L PSD, ZF-6S650, 3.73, 35x12.5-18, 4.5" Lift