Info needed on 308 oil pressure sending unit

I am working on a project to possibly make the 308 oil pressure gauge accurate. The missing piece of information is the mechanical thread sizes involved. Without dismantling my car I thought someone might know the answers here on FChat.
When I look at the oil pressure sending unit it appears to have a thread adapter on it. If so, I would like to know the diameter/pitch/style of each thread. The male thread into the oil filter base I have researched to possibly be M18x1.5. I have not found what the male thread of the senor is (assuming that the piece I am looking at is an adaptor)

Thanks for any info
Art

 

m18 x 1.5 on my original sender - 1981 gtsi. jon s

 

.. and another thread. Have ya got it solved? I could drive over… ;-)