I am getting towards the end of a major project of installing a new factory rebuild Lycoming IO-540 and at the same time installing a new Electronics International CGR-30P engine monitor that is certified as the "primary" monitor BUT I am keeping my old analog gauge cluster as a redundant means of monitoring the engine and fuel. The CGR-30P of course comes with new bayonet style CHT probes / sensors. QUESTION: what is the best route to go in regard to a CHT probe for the old analog CHT conventional gauge in the original gauge pack? I was thinking about using a spark plug gasket type gauge, but I was not sure what type (J or K) or if it made a difference? I realize that the old analog gauge will not be accurate, but after some use, I can determine the delta of it and the reading shown on the CGR-30P as shown for the #5 cylinder and use that ratio if I ever had to rely on the analog gauge for some reason (the failure of the primary CGR-30P unit). I know that some others have done the exact same thing I have - install a new primary engine monitor but keep the old gauges - so I was looking for a little guidance on the CHT probe for the old gauge.