I bought my EGT probes from Stein Air - they came with the Engine Monitor System (EMS). I learned from the Cozy forum that the EGT probes should be mounted at same distance from its corresponding exhaust port. Being careful to the advice, I did the following:
I used a strip of paper and draw a mark 4" from the end. Then I butt the paper strip against the exhaust port and place my mark onto the exhaust pipe.
Then I made a paper protractor and with the help of my miniature bubble level, I complete the cross hair (mark) on the exhaust pipe. The mark provided me the distance and level of the probe.
Holes were drilled accordingly...and
Exhausted Gas Temperature probes are mounted.