when I switch the engine off, after running 5 minutes or 50 minutes, with the Temperature Indication slightly below mid-Green Band, the Temperature Needle will be at the bottom, though I know there is ample residual heat to indicate 1/4 or whatever.

I just find it strange the Temperature Needle doesn't reflect the residual heat, that I am sure would scald a person.

The Temperature rises to its normal indication slightly below mid-Green Band, after a couple minutes running, or less.

Thermostat is a new Volvo OEM Thermostat.

It has done it before I replaced the Engine wiring harness, as well as after.
In fact, I am nit-picking, because it has always indicated so. Everything
else is normal and works well. The Carburetted B21A Engine starts with little more a flick of the key, in the cold weather south of the Equator. Cannot say that about my old B21E Fuel Injected Engine, and I spent more time and money.

The Temperature Sender seems to be a real bitch to remove from its location beneath the Intake Manifold, without removing the Intake Manifold.

Any ideas?