The air horns were made by destroying a perfectly usefull air cleaner base. This is all that's left.
The coolant fitting at the front end of the manifold isn't the original, but as long as it takes coolant to the inlet side of the water pump, it will be fine.

The two thick insulator blocks, seen with the springs at right of photo, are normally seen with the twin carbs that came on the larger L series engines. The correct thin insulators are still on the manifold. These thicker ones can be used, but need the longer studs from the L series manifold to make it all work.

must have been a common mod, mine have the same trumpet mod, I have the lid, but mine were fitted with small K&N's on each trumpet.. ...

Yea, it does look like the air horns where cut out of something.

I plan on blocking the water to the intake.

Good eye dodgeman. If the thin ones are sufficient, I will definately use those. As you know, we (US LHD) sometimes have clearance issues with the carbs and master cylinder.
I am interested in a close up pic of the linkages. I got a hand full of pieces and springs. I'm not exactly sure how all that goes together.

It looks like you have everything from what I can see. It will all fall together once you start picking up the pieces & start puting it all together.

As for the coolant fitting, I do not recomend blocking it if this is to be a street engine as the coolant flow is intended to heat the runners & ensure that any liquid gasoline that tends to gather on the bottom of manifolds during cold seasons, is turned to vapour & burned, thereby making power, instead of finding its way into the cylinders to wash the oil from the walls, then into the oil pan to dilute the oil.

If the fuel isn't fully vaporised, then the mixture runs lean & you need to richen up to compensate, causing needlessly high fuel consumption & poluting the air with unburned hydrocarbons.

For street use, leave the manifold heat in place as it does not rob power, but provides a well balanced street induction that will be a joy to drive. Those clever little Datsun engineers knew what they were doing.

Oh yeah, that fitting takes the coolant 'out' of the manifold & into the intake side of the water pump. Coolant enters the manifold through the four holes under the inlet ports. They were placed there, & made that big for a good reason.

Standard carb overhaul parts or kits will be the same as the L series items which I believe were available in the U.S.

Your manifold seems to be a B210 GX casting, but it seems not to have been machined for some of the fittings that were used on the definitive B210 GX models. Most interesting.