id recommend the dual 12" fans, you will cover more area of the rad. when you dont have a shroud a single fan is always at a disavantage.
a trip to your local u-pull junkyard may also be a good idea, try to find ones for rads the same size as yours. I found 95 altima fans to be a near match, and with a bit of hacking got them to fit. The great thing is you can keep the shroud and they have hi and lo settings. rig it up for constant lo, then when you have hi temps have it switch to hi. and with those fans hi was way overpowered

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