Perkins 4-108 Water Outlets

[Tashtego]

I have a Perkins 4-108 and a question about where to mount a pair of water temperature sensors. I have had the engine rebuilt and asked the rebuilder to add the valves to connect to my hot water heater. One valve was installed in the hole on the top of the block that previously held the water temperature sensor. What to do? I added a 2" nipple (to clear the thermostat housing) and a Tee and put the valve on one side and the temperature sensor on the other. OK But I also have a warning system with a buzzer for oil pressure and water temperature. Where to put the temperature warning sensor? The valve and sensor are screwed into a hole on the front, port side of the block next to the thermostat housing. Near to that on the right side of the front of the block is another hole, filled with a threaded plug. At last to the question! Can I unscrew the plug and install another water temperature sensor? Does that hole go into the water jacket just like the one the current valve and sensor is screwed into? Is there anything in there that a sensor could damage? Thanks for your help.
PS What I call the block may actually be the head. I'm not near the boat and can't tell from here.