You can see the upper hose crosses over the plug for temp sensor

 

Due to the plug next to tstat, this is probably why they put it in the head

 

That blue plug is a coolant source, try the sender there.

 

You can try ther blue plug port, but there is not a coolant run, like up front, and its at the rear of the block/head and still going to indicate hotter.
But try it, can't hurt.

 

The coolant from the block enters the head at the rear and flows forward towards the tstat, so there is flow back there and it hasn't cooled the head yet so it might show a cooler reading.

 

GM put it in the head for a reason.
personally I would rather monitor head temperature, especially aluminum heads .
if your engine gets TO HOT, the head gasket is going to pop
is there really going to be that much difference in temperature of the distance the water travels from the intake to the head?

 

You could install one these and install sensor in the front coolant passage
https://www.summitracing.com/parts/r...make/chevrolet

 

Back in the days of idiot lights, it made perfect sense to have the sensor in the head to warn you if/when it got too hot, because the heads get hotter than the rest.

 

I want to try and put the sensor next to t-stat. Below is what it looks like now, thanking if this style housing that will guve me room to install the sensor. Having an issue finding a upper hose now, been searching. Any suggestions and or link for that hose? How is everyone else using that front manifold plug? Thanks in advance.