I think you will have a lot more success at much lower cost by going to an aftermarket sender and gauge. Your temperature sensor on the engine is a switch, not a temperature sending unit (a resistor that varies with temperature). Also, the wire going to your instrument panel is wired to a light, not the upper right area where the temperature gage is mounted on the Deluxe model. If you pay the price of a complete instrument panel, you have no way of knowing if the wiring harness on the tractor will match your new instrument panel. You'd have to do a wire-by-wire check of the schematic and you'd surely have to add a wire for the sending unit or rewire your harness for the light wire to be used as the temperature gage wire.
Can you see how complex this is getting? I think I would look for an aftermarket gage that you cold mount somewhere convenient. You could cut a hole in the cowling below the instrument panel (the black one) and mount the gage there in a very professional and neat way.
Finally, I think if I were in your situation, I'd just buy an inexpensive IR thermometer to carry with me on the tractor. When I want to check temperature, I'd stop and do it with the IR. By doing it that way, you can use the IR for hydraulic temperature as well. It's very flexible and will leave your tractor without modification.
