"IF installed right" you should have no problems. I have a couple friends that paid me to install a 3.8 taurus fan (yes the 2 speed version - I found like 5 at the junkyard). All told, none of them see the temp guage really go above the 200 mark let alone come close to it really (referring to last summer). I know it's still a little cool out but the needle on my temp guage doesn't get above about 1/8 of the way, so I don't know what happened to you - maybe defective fan or poor sealing/install?
Try the fordmuscle.com website as they have a ton of writeups on many mustang mods and such.
BTW - how much power were you trying to cool, seeing as it was used on a so called track only car? A fan like this should only be used for a car in the neighborhood of 250 hp or less really. Anything vastly more is asking too much.