Overheating Problem?

Finally almost got all the bugs out of my new build but I am having a cooling issue. It idles fine but it gets hot according to my mechanical water guage. I'm seeing over 200 if I let it idle for about 15 mins. I have the stock fan which appears to spin ok and the whole cooling system has been replaced with the exception of the heater core. I also have a 3g alternator with the stock pully it came with but I have the water and crank pully underdriven, could this be my problem? Is there anyway I can test my 180 thermostat within the car without taking it out? Any help is greatly appreiciated. Please reference this link for all my build stats ____
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http://www.stangnet.com/mustang-forums/threads/need-some-motivation.851972/#post-8589495

lrs 180 t stat

Swapped out my stock set of pulleys and all is well. Upon noticing, the fan speed was much lower with the udp's which probably meant that my wp wasnt spinning not nearly as much as it should have been