I haven't seen anything asked anywhere on this yet. I have drop siding spec'd. My concrete guy is setting 1x1s (treated) into the wall that will terminate 6" above grade. I am using regular 1x4s for vertical furring strips and think I should use treated for the lengths that sit on top of the concrete. Yes?

Also, how does one affix cor-a-vent there? Or do I mount it higher up where I can tie it into the wall sheathing? But then I wonder if critters will make a nest in the areas between the siding and concrete. Maybe I'll tag some screen netting there at the bottom and cor-a-vent across the bottom of the sheathing.

Let me make sure I understand. You are letting in the verticals and putting horizontals on them. At the bottom just get some screen or wire mesh and wrap it up the siding vertical before nailing them and up the horizontal then nail it in place, in other words tack the screen or sandwich it in the rain plane. Do the same at top. You want vertical channels that have a gap to the concrete at bottom to drain water to flashing that deflects it away from the building. You could use another screen from the bottom horizontal to concrete to stop nest I guess as long as debris can not accumulate and clog it up like gutters. If you want to use cora-vent follow their instructions its on their website.

In the foundation wall, there are 1x1 treated wood strips inset vertically. I will be screwing in with headlocks the furring strip on top (also vertically), and putting siding across. I am curious whether the furring strips on the foundation wall (concrete portion o fthe wall) should be treated as well since they are in contact with the concrete. For the CorAVent, it will have to sit between the furring strips where there is only concrete. So how does one affix it there? I can just put in the netting/screening like you say, I suppose, and forego the CorAVent product.

fasten it through your siding?

Well then I'll see those nails...i think what I'll do is use screen on the drop siding bottom, and coravent above where the framing starts at TOF

I need to revisit this as plumbing/hvac/elec starting next week so siding will be soon afterward. To explain better. the concrete foundation/walls are exposed 4 feet above grade due to grading/slope of the lot. City requires I put siding here. Embedded in the concrete were 2x2 nailers (treated) vertically inset every 16". I have 1.5in XPS foam on the framed walls. So I need to build out the siding over the concrete and need to do this soon.

I am thinking to use treated 1x4s to nail/screw horizontally across the 2x2 nailers embedded in the concrete. I would run these treated 2x4s from the corners 16' and butt them to cover the full length. On top of that, I would screw in my 1x4 furring strips vertically. Between the treated 2x4s I could insert some rigid foam there ripped on a table saw. I would probably need some deck screws about 3.5in in length to go through the FS, the treated 2x4 and into the 2x2 in the concrete to hold it. Maybe screw it every 6 inches.

Consider just using continuous foam, no 2x4s. Less work, less thermal bridging. When glued and screwed, wood/foam/wood is quite strong in terms of supporting loads.