A cooler with a fan would be beneficial if you get in a situation where you are not moving fast enough to get good air flow. I would like to have one incase of that. I say just go ahead and find a good place to mount it and see how it works. BTW one of the Trucool 40,000# coolers I bought fits in the factory location. It was a tight fit and a pain to install but seems to work pretty good. It is the same size as the one I mounted behind my bumper but it has long brackets made onto it so it will bolt in beneath the inner cooler. Seems like the plain one was around $100 and the other around $120 new on the net.
Ford sends an inline filter with the tranny but no cooler, they do require that you change the factory cooler before they will honor the warranty.