On 'Balck Betty' when I first got 'er she had a radiator fin probe on an existing pusher fan. Over the course of the next two months the downtube next to the probe deveoped a small leak (dissimilar metals, fibration, etc). So I searched for another way, I found this double ported radiator hose sleeve from Summit
and now with my newer Merc Mystique dual fan assy. I am controlling the fans independantly. This cleared up a long standing overheating issue in the summertime and I'm ever grateful to JeepHammer amongst others that lended their support in helping me get a handle on this thing.