Truck Repair: S 10 coolant temperature fluctuations, coolant temperature, fan clutch

Question
I replaced the head on my 1995 S10 2.2L PU with a rebuilt head. I replaced the thermostat as recommended and had about a 30 degree swing in the temperature. I exchanged it for another one and it still fluctuates. It is a $5.00 thermostat, but that is all my local parts store had. If I run it without a thermostat the temperature stays steady at about 150 degrees. Do I need to get a better thermostat or could it be some thing else?  

Answer
Hi Keith,
That cheap one would probably be fine.
Sounds like the cooling system is working great, so as long as the thermostat opens, I think you will be in good shape.
You may want to check the fan clutch, to make sure it isn't locked engaged, but if it spins ok, I wouldn't worry about that 30 degree fluctuation.
Van