Hi Bob,
I do not know if your engine is a dry sump or wet sump.
However, in a dry sump engine the
oil temp thermocouple should be located in the dry sump tank.
In a wet sump engine the
oil temp thermocouple should be located in the
oil pan.
It has been my experience that a thermocouple located in a flow area does not give reliable readings. This is probably due to heat exchange rates and boundry effects.
Of course, if you have a wet sump in your car, you probably do not wish to remove the pan to install the proper fitting. Therefore, you are better off in the filter location as is current.
This will give you the best reading as this would be the high temp side and after the cooler would be the low temp side.
Hope this helps,