SUN temperature sending unit

[SD 396]

I am new to this site but saw this post and thought I would help here if I could.
I had an electrical engineer look at this sending unit a few years ago and he told me it is not a typical ohms resistance sending unit. I was looking into getting them made before "Chiper" had them. He said the cost would be very high. I would think that the ones that chiper sells on ebay would be worth it if they work. He only has the 1/8" thread so you would have to use an adaptor. The Sun part numbers for the three available sending units are WTS-125, WTS-375 and WTS-500. 1/8", 3/8" and 1/2".
I sent one gauge to Williamsons in AK and had it converted to mechanical. Works great but has the newer spring would capillary tube.