At variuos times reviewing 240Z maintenance literature, I will see a reference to an intake manifold coolant thermostat. My 72 currently does not have this thermostat. Does anyone have an opinion on this item?

If you have bypassed the water going to the intake it is not needed. However, if you have water going to your intake you definately should have it. It cuts off the water supply at a certain temp, and without it, you may be putting too much heat in the intake and it may cause you to vapor lock. I personally would rather not have any water at all, it will take a little longer to warm up but the cooler the intake charge the better the engine will run.

You can plug off the water with a simple blind rivet in the line where it connects to the water control valve at the back of the intake or do away with them altogether. Are you positive it doesn't have it? It is the "nipple" that the hard line connects to at the back of the intake. About an inch or so long.