Oil Pressure Gauge

[utahseries]

Due to my OCD, I'm adding an oil pressure gauge to my 91 RRC.. The thread for the sender is 1/8 NPT.. I'd love to be able to just get an adapter and put it in one of the existing holes in the oil filter housing, but I can't afford to have the car down for long enough to drain the oil and find out what thread the existing holes in the housing are.. Anybody know what they are off the top of their heads? (I'd like to get the necessary adapter and have it ready for the next oil change.. And I DON'T want to use a "sandwich" to mount the sender)
Thanks.

[o2batsea]

I want to say the ports on the adapter are NPT, but the exact size I am not sure if it's 1/2

[utahseries]

Thank you.. I was also thinking they were NPT, but it looks like I'll just have to pull one of the bolts out and find out what the size is for sure.

[o2batsea]

Yeh everything on the engine is SAE, not metric.