Your engine and cooling system both sound okay, it just sounds like the cooling system lacks the capacity at idle to cool the coolant. The value of a fan shroud as mentioned by FWD is enormous, don't discount it. I would suggest you get a $60 infrared temp gun like this
Micro Temp MT-PRO - Spark Industries Micro Temp Digital Infrared Pyrometers - Overview - SummitRacing.com and check your upper and lower radiator temps and check temps in the path of the fan and then outside the fan path. If you don't see 30-40 degree reductions from the entry and exit point if your radiator, your fan/shroud isn't doing the job. And if the temps outside the fan path are considerably higher, then the shroud or lack thereof is likely a contributing factor.
As for pulley size and pump circulation, I wouldn't go there yet. If you start trying to circulate the water faster, you lesses the amount of time it sits in the radiator to be cooled.