Help...!!

I ordered an adapter (10.0x1) from ACS.  This is the size I got off this list as to what is needed for the oil pressure gauge post.  Well... it doesn't fit, the threads are finer on the oil pressure gauge sender unit.  Sooo.. what is the real thread size for the Oil pressure gauge port on the 13B?  What is a good source for an adapter to go from the oil pressure port to pipe thread?

Wendell