<< Mine is starting to run hot when on highway for a steady run. >>
If it's heating up at highway speed, it has nothing to do with your fan or fan clutch - neither of them have any effect at road speeds. You have other issues, most likely radiator-related.
Define "run hot" - have you checked coolant temp with an I.R. gun on the radiator inlet hose just above the thermostat housing vs. the temp gauge so you know what the gauge is really telling you? Does it puke coolant out of the radiator overflow hose?
You might read this article on classic cooling systems - I wrote it for 60's Corvettes, but the principles are the same:
http://www.lbfun.com/warehouse/tech_info/cooling%20system/cooling.pdf
