I wanted to buy a device to measure how hot the exhaust headers get. How high of one would i need?

 

The Fluke company makes quality thermocouple monitors. They have a model 52(?) that will read 2 channels with hold and record capabilities. K couples will more than cover what you need. J couples will just about get you to 1400f so you might max them out whereas K will go to 2500f so most of your reading will be in their mid-range. ISTR seeing them at Summit but I would try an instrument/electronics supply house first.

 

Are you trying to measure the tube metal temperature, or the exhaust gas temperature?

 

External tube temperature.