If you buy one of those "universal" fans, don't use those things that go through the radiator to mount it. They're easy, but not worth it. With the weight and vibration of the fan they will eventually cut through the radiator core (I speak from experience). Make some brackets up from that perforated steel strip you can get at Home Despot or the hardware store.
Or you could do what i did on my old Grand prix and hardwire the secondary fan (this had 2 fans, one that came on at lower temps and one that came on at like 225*) Anyway i wired the 225* fan to a switch by grounding out the relay thingy and left it on all the time, except on cold mornings if i didnt turn off the fan it would take about an hour to warm up
Look in Jegs get the Perma Cool High Performance 16" works great moves MAD air, and BTW who the fu*k cares if it WILL fit under the shroud take the bottom off and never use it again and cut the actual "fan shroud" off the top and just use it for a radiator support........a grinder with a cut-off wheel works the best on the plastic.....the fan shroud is just there to make the sh*tty clutch fan pull air through the radiator.........there is much more room under the hood with out it........and it is actually restrictive with the elect. fan anyway. :stupid::bash: :twak: