Found my dads original 1971 duster!

70SwingerGuy said
A gauge like that uses a sending unit that threads into the intake manifold and is usually permanently mounted in the car, usually under the dash, the signal from the sending unit is carried to the gauge by a wire, it is not possible to thread it directly into the engine. Where is the sending unit located that you are using right now? Ive never seen an autometer used as a temporary gauge, but Im sure you could make something work, kind of pricey though for something that would only be used briefly.

A gauge like that is typically hung down low under the dash in a non-intrusive manner. And as @70SwingerGuy notes, you only need to route a single wire from the sender in the intake manifold to the gauge inside.

Also as mentioned, be sure to get a gauge that has good differentiation to show temps where you want it to be - like between 160 and 200F. The gauge he references is good but Autometer has many styles for you to pick from if you prefer a different look (I use the Sport-Comp series).