Well, I dug and dug and dug some more. I'm sure I seen that old temp sensor when looking for something else not long ago.
so I kept digging. Thinking I really need to organise this stuff one day. And finally.....

This always worked fine. I'll clean it up and give it a go. It's original as is the gauge so hopefully....

 

OK, so I spent some time cleaning this old gunky switch up. Got her looking almost like new again.
And with a drain pan on the floor under the area of this sender, and a dab of thread sealant high up on the threads. I removed the replacement sensor and quickly reinstalled my old one. Losing just a little bit of coolant. I then replaced the heat shielding on the green wire as the original shielding was looking a bit dog eared. I had some really nice wire heat shielding that was left over from a previous project. Then crimped on a new terminal. The original was looking it's age.
fired her up with my EFI hand-held set on engine temp and sat in the car to monitor both gauges. As I am not into posting video's I will share a series of photos.





in this last photo on the far left side you can see my fan indicator light is lit up. A little something I added to the car. The rad cooling fans are programmed to come on at 195. As you can see by the lit up little yellow fan they are running and the dash is not reading 235 as it was before when my fans kicked on.
I'm calling this one a win!
Thanks to everyone for their suggestions and advice.
As it turns out. Nothing wrong with the location of my EFI temp sensor. It was an issue that had me scratching my head as the 2 gauges agreed sometimes, but not all the time, as in at different temps. Now it looks like they are very close to one another. Shame we can't seem to get an accurate replacement temp sensor. I hope my original lasts a long time.