Temp sensor, D head, thread type?

[Nessmuk]

Anyone know what thread type the sensor in the front of the drivers side head is?
It's above the injector, and at the front.
I want to put a manual gauge in it.

 

[Jaryd]

I went to advance auto to get me a mechanical gauge to make sure my dash gauge was accurate and it had the bushing I needed in it. It looks close to 3/8" or whatever that is in metric.

 

[3500GMC]

3/8 NPT 'national pipe thread'

 

[Nessmuk]

Bought another cheap gauge, will try again.