I have a Flexalite kit and it cools great in the 100+ degree Texas heat. I don't tow what some might consider heavy but been towing a boat and tractor with no problems with cooling or ac.
Flexalite is too pricey for me...
I have been doing some research on electric fans.
Ford Taurus from 1988 to 1995 have 16" fans that do 4500cfm EACH!!
Lincoln Mark VIII fans do 5000cfm but are to big to mount 2 of them.
If you look around, you can pick up new ones for under $100, and a Summit Dual harness for $60.
Now the Flexalite drop in is rated at 5500cfm IIRC.
If you do 2 taurus fans thats 9000cfm. For half the price.
If you intend to tow, forget electric fans. Nobody makes a fan that will move the CFM of a stocker.