(quoted from post at 21:31:47 03/05/18) Barry is right, electrical gauge is a common replacement for the mechanical temperature gauge in SW cluster panels. You can use any 2" or 2-1/8" SW 240-33 ohm resistance gauge as in pic, doesn't matter what face plate gas, oil, temp, SW 240-33 ohm resistance gauges have the same movement, just use different type senders. The gauges are obsolete but are often ebay items. The two in the pic are the range you want to fit in the cluster temp gauge opening.
Your gas gauge has the same movement as the 2 gauges in the pic. You will probably end up buying a used gauge that may be 40-50 or more years old, you can use the your gas gauge wiring and float to check it out or wire it up separately before going to all the work of installing it. Looking at the back of the gauge the right terminal is switched 12v power to the movement, the left terminal is out to the sender, the ground to complete the 12v circuit may be a third terminal or more commonly grounds through the gauge case.
You need to drill holes for the gauge terminals in the pod. On the replacement gauge cut the bezel and carefully remove the movement from the case. Replace the existing faceplate with you Case temperature faceplate. You will need to drill new holes lower on the Case temp faceplate to orient correctly in the dash opening. The gauge movement ground is a copper strip on the back of the movement that is in good contact with the metal back of the pod. The terminals must be insulated from the pod where they pass through the holes.
The correct temperature sender is Case p/n A21462. I use to buy the sender at Napa but can't find the Napa nr, they should be able to cross-ref for you, 240-33 ohm senders use to be very common but you need the one that threads into your engine which all the ones I have done were 1/2" npt.
Last pic is the electrical movement for SW 240-33 ohm resistance gauge.
Been 7-8 years since I have done one of the Temp gauge swaps, don't have many good pics, or can't find them.