Engine rebuild

Regarding the emissions air injection tubes for the exhaust manifolds: I can find the tubes online to buy, but I cannot find the extension tubes that connected to the air tubes and went directly inside the manifolds. Do I need those extensions, or just the main air tubes as shown in my earlier pics of the exhaust manifolds? The pics I posted earlier show the extender tubes in question.

I need to replace one of my exhaust manifolds; should I get oem cast iron, or put on some headers? Maybe these, if they'll fit? https://www.summitracing.com/parts/sum-g9011/make/chevrolet/model/c20/submodel/silverado/year/1984

Great, thank you. If we do headers, how does that affect the AIR injection stuff. Does all of that go away? I just bolt on the headers and call it good?

I would like to paint the heads before installing them on the block. I got them back from the machine shop, fully assembled (valves, springs, etc.), And clean cast iron. Am I okay to paint them and then bake them to cure them, or should I just paint them and install them, and let the engine heat (when running) cure them?

Power steering pump re-use, or buy a different one?

Can you tell me what the small pulley is used for, to the left of the water pump? Is that the 'air compressor' for the exhaust air system? Or something else?

Any idea what this vacuum part is? It's on the intake manifold, right next to the thermostat. Obviously the tubing is wrong, but I'm trying to find out what it is, and if I need to replace it.

Battery/power/ground cables.I need to replace mine on the truck. Can you give me an idea of what, how many, how long, gauge, etc?

The radiator we pulled out was a 4-row core; LMC says I need a 1-row core. Should I replace what I had, or get the cheaper, less-core, unit? Any pros/cons?

Can you tell me what this part is? It seems like some sort of vacuum thing..?