Actually, Bill Williamson at RD Radiator advised me
against putting an auxilliary fan on as it would actually cause a decrease in air flow as it actually blocks airflow and only about 30% gets through.
http://www.vehicross.info/forums/sho...1&postcount=19
And it was the same for me basically, my problem wasn't fully resolved either until I replaced the fan clutch (and redesigned fan blade).
I went with OEM cuz somebody mentioned they'd tried several aftermarket f.c.'s and they'd and their overheating wasn't resolved until they tried the OEM f.c. Think it was VXorado.