Well, thermal fan for engine is a good idea, i had it before. Basicly less stress for the water pump, engine make a bit more power but you definately NEED SHROUD for air to concentrate in a particula area.
There is a down side to it, if the switch/relay or whatever that trigger the fan to come on fail to work, you know the result. I havn't seen a reliable controller for awhile.
One thing i just didn't understand was that i had a brand new thermal switch from Nissan and that day when my car heat up to 97c it still didn't trigger my aircon fan where it should.
I've seen EL Falcon on a R34GTR before, this guy is a genius ( YLWGTR ), he even had a circuit board made up to control the fan.