OK, well I came up with a workaround
First, this gauge:
https://www.amazon.com/gp/product/B000EVU8YI
I moved the original temperature sender off to the side and zip-tied it mostly out of view (in a much better way than depicted here). I then coiled a dark blue wire around the old copper line and through the firewall.
The light in the gauge is tied to the same light for the clock.
I put that gauge on a hinge and a small magnet tethered by a fishing line that allows me to tuck the hinged gauge up and out of regular view. But, when I need to see the temp of the coolant, I can easily pull the magnetic leash off of the wiper motor housing so the gauge is visible plenty for me to monitor engine temp.
I don't mind that the gauge is upside down - I just need to just be able to know what the temp is. And, at the angle the gauge sits with the hinge anchored to the bottom screws of the control sliders, it's hard to see right-side up.
