JPI EMD 760 modification question
 

I have a 1979 P337/H that originally had the GEM EGT monitors. Years ago they were replaced by a JPI 760. Reading thru the logs/337's I was unable to determine if the original GEM EGT probes were used or even allowed in this modification. However, my question is; I still have the dual mixture adjustment gauge (EGT), in the aircraft. The rear engine needle corresponds to what the JPI reads when running. However the front needle is dead. My question is does the original single EGT probe pull from the JPI probe(s)? Or is it a completely different sensor. Looking at my front and rear engine exhaust stacks I only find one EGT probe for each cylinder and not a second one for the old original equipment EGT probe per engine.
I am just trying to get the front EGT to register on the old gauge like the back does. Ideas?

The original probes are normally in the junction area where the 3 tubes come together and only on one side of the engine.