I live in AZ and my 89 GT is doing the exact same thing. My setup includes a fluidyne aluminum radiator, brand new stock fan, new heavy-duty fan clutch, silicon hoses, and 180* thermostat. I took off the underdrive pulleys and bought some stock ones. I just bought a new radiator cap that I am putting on in a few minutes, but I have not pressure tested the cooling system. My oil is not milky...I have an autometer temp guage and it consistently measures about 190* on the freeway with a/c on in 105-110* AZ weather. However, if I idle for about 5-10mins with the a/c on it will climb to 220*. Originally, before I bought a new stock fan/fan clutch, I bought a Mark VIII fan, but I didn't want to do a 3rd gen alternator to run it (too much $). My question is:
Is a 93 cobra grill insert + some type of junkyard pusher fan from an a/c condenser a feasible option? Or will it obstruct flow at 40+mph? And yes, I realize that all of the money I have spent could have given me the 3rd gen alt. upgrade already, but I already have wasted enough money on this setup!
Also, does anyone know where to get a nice reliable 180* T-stat that opens all the way or should I go down to 160*?