63 Plymouth oil sending switch thread size.

[Wallus57]

Good day folks.
I was going to install a mechanical oil pressure gauge in my Savoy but when I pulled out the old switch I found that the threads are much larger than the later ones, somewhere around 5/8" diameter. Does anyone know the thread and pitch (probably NPT yes?) of these old switches. I'll need to use It as a reducer for the new oil tube fittings.
Thanks, Wally

 

[493 Mike]

1/4" or 3/8" NPT.
Mike

 

[JonR]

I believe it's 3/8" NPT. I had to change my switch and now I'm going to add a gauge and keep the switch.