I've got one of these "non-Taco-plate" type of oil temp plates. I've had a small but persistent oil leak that seems to come right from where the sending unit threads into the plate. There wasn't any sealing ring or anything else on the sending unit. What should be there to keep things dry? I purchased one of the seals that is for early temp sending units, but I'm not convinced it's going to work (it's under the sending unit in the picture below).

I've got the rubber outer seal and the tiny crush washers for the bolts.

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Maybe this???

https://www.permatex.com/products/thread-co...lant-with-ptfe/

Yeah, I was thinking something like a permatex solution, unless there's a ready made crush washer or something.

I've used this product with very good results over the years. It takes very little to do the job. I burnish threads of stubborn sending units and crush washers, seals, and so on. Not glopping it on mind you, the purpose is to take care of imperfections in sealing surfaces to aid the standard seals and washers, not to replace them. In my experience if you are wiping off after tightening you did it wrong.

I sealed my 912 engine about 4 years ago. Including many short drives and a cross country trip from Texas to California, still no drips, no leaks.

https://www.permatex.com/products/gasketing...gasket-maker-4/