Thanks for the comments. Yes it is in the factory round housing for the gauge cluster and there was a electric sender although it was at the front of the engine not in the manifold. The gauge housing has a round hole behind the temp gauge unlike the oil pressure gauge which is square to hold it in position while tightening the line to it. The back of the replacement gauge I bought (which obviously is mechanical ) is square like the OP gauge. I don't have a problem using the mechanical gauge however I will have to modify the housing to accept it. Was yours this way Jim K? I imagine that my current gauge can be restored. I'm not sure if it works but the needle has broken off. That's why I wanted to replace it.
Rob