It's real hard to get the air flow with an electric engine fan that you can with the OE belt-driven fan. Not to mention the reason some want to convert to electric fans is that mythical increase in HP. There is no free lunch where turning a fan is concerned, an electric fan places a load on the engine too since the alternator becomes harder to turn with the added load from an electric fan.
Assuming you have an automatic transmission, Derale (which I did an installation review of) and B&M are the leaders in active (with electric fan) transmission coolers. Either would be a good choice. The Derale writeup is at http://www.wranglerforum.com/f5/keep...er-110676.html