This is the current temp sensor location, it's 1/2 threads. No problem putting the temperature sensor there for the ECM, it's 3/8 thread.
The problem, the temp sensor for the temperature Gauge is 1/2 thread, If I drill and tap that bung in the neck, I'm afraid there won't be much left and it will crack when tightening.
Gauge Sender installed in original location
New ECM sensor in water neck before thermostat, there is a constant flow here , Thread
Size 3/8, was pretty easy to tap.