Temp gauge accuracy

Cheap way. BUT a refrigeration style thermometer, you can get a decent digi one for 20 bucks

http://viot.us/images/WT5.jpg

There are all kinds of these. Hundreds. Maybe thousands

CHECK IT FOR ACCURACY

Easy Boil a can of water on the kitchen range. Unless you live in Denver this should read very close to 212 degrees that's F as in Farenheit.

TAPE it to the bottom THE BOTTOM of your TOP radiator hose.

Improvise some insulation. This can be a towel. TAPE the towel/ insulation on there.

Be absolutely sure the fan or belts is not going to eat any of it

Run the car until stable and take some comparison readings.