My experience has been temperatures at both locations are close to the same at road speed RPM, like 1500-2500, but coolant at the cylinder head port gets hotter at idle.
Also, I like to know the coolant temperature near the t-stat, since that's what regulates coolant flow.
To the OP: I'd suggest getting a good quality mechanical gauge to see what really going on, because external surfaces are going to be a little less than actual coolant temperature. I did just that on a 69 pickup to determine the temperatures at various places on the unmarked gauge. Turns out at 180 degrees, the needle was well to the left of center. I ended up changing the value of the shunt resistor so 180 is almost at the center of the gauge.