It's your tractor and your $$$ so do what you want. I'd agree the 9N, 2N, 8N never had had a production run of temp gauges, and no need to install one now. The exception was for the NAN models only. At one time Ford was going to add one -look at the LH front top side of the cylinder head and some late models had the cast boss where the sensor was going to be mounted. MPC's show the 39-47 dash panel with the NAN Temp Gauge cutout shown. Read Bruce(VA)'s article in the N-News on radiators, coolant, and thermostats. Most overheating issues are due to overfilling or underfilling the coolant level in the radiator. Always use a thermostat in the upper hose. Yes, the temperature gauge was used on the 9NAN; 2NAN; and 8NAN tractors only. The TEMPERATURE GAUGE was fitted on the RH lower dash panel, at the 5 O'Clock position below the OIL PRESSURE GAUGE. The original drawing for the dash shows the hole location cutout with: "NOTE - TO MAKE 9N-AN AND 2N-AN ADD THIS HOLE". The original drawing for the gauge faceplate, 9NAN-10888, shows: "WARNING: ONLY USE HEAVY FUEL WHEN NEEDLE IS ON THE GREEN". These drawings show the temp gauge was released in July, 1941 on the TVO/Kerosene burning NAN models only. WE have the 9NAN Manual and the 8NAN Manual in our library. The -AN models used a special manifold and the vaporizer unit. The -AN models were almost all exported to the UK, Europe, and Australia.
FORD 39-47 STEERING & DASH WITH NAN TEMP GAUGE: