Where to install Temp gauge on the Slant

1966 ddart \6. Having issues with stock gauge, trying to get it going in another thread. In the meantime, where would I install a mechanical Temp gauge? I do see 2 unused connectors on the top of the new radiator I installed. Would I screw the sensor into one of those locations? Or is there somewhere else on the engine that I could use? Also any advice on which gauge to use and where to find it? I have just had the engine rebuilt, and he says if it overheats he wont be responsible for it if my temp gauge is not fixed (by me).
So this is a priority at the moment.