Cooling Fan Options

I have not been running a cooling fan since I replaced the radiator last November.  Probably cheap and lazy, but it never made it back in the car after a crash took it out.  As the summer heats up and I'm heading down to Buttonwillow at the end of the month to run a (very hot) late June race, I'm thinking about putting the fan back in...just to keep it a bit cooler during idling on the grid, etc.  Does anyone have suggestions on the easiest most efficient install?  Is just putting another stock unit in the best or is there something else that is legal and works better?  I'm running the SuperMiata radiator.  Thanks!

Yes.  I just re-read the rule.  I misread last time and thought and aftermarket shroud was allowed, but I just read it again and it says it may be modified.  Thanks.