Thanks Allen
And thanks to Billy for posting for me.
The first place I went to install the temp sensor was the head.
But, the sensor auto meter sent w/ the gauge was just a hair to small and the wrong thread. An adaptar is out of the question, because of the size being so close.
If the opening was larger it would be no problem finding an adaptar fitting.

So a 98 ls1 temp sensor will work.
Will I have to buy a new connector and will the wire color be the same?