Forgotten.... What thread size are head studs into the block ?

[Lynn Eades]

Here is a pic of how Henry set it up. One is variable and one is a switch.
(two terminal and one terminal, are wired in series)
I will also include a bit on the oil pressure sender. Be aware that there are two types of different resistance. you need the one to match your guage. The early one is harder to find. (I think the later one has "80" in a circle stamped on the face of the brass square.