Temperature & water pressure guages

[Randy Skopinski]

I have a 2003 90 HP Johnson OB and I am going to add a temperature & water pressure gauges. Looking at both of the heads there is one clean drilled & tapped blind hole ( looks like 3/8- 24 NF) and the other looks like it has a 1/8-NPT plug plugging it. As far as temperature I like to monitor the actual head metal temperature and not the cooling water which is not necessarily indicative of what is going on. When I look at temperature sending units most come with NPT threads which indicates to me they are going to monitor water temp and not the head metal temp.
Where is the best place to tap in to read the water pressure?