To answer your questions:
There are a few wires running right around that area that are all sort of the same color (age changes white wires to a yellow color). You have a wire leading from the back of your alternator to your choke. A line is spliced in and runs to the choke relay (relay mounted directly below your voltage regulator on your right apron). Your throttle position sensor wires run through there, but I doubt that's it. Your charging harness is back there too, but other than the choke power wire, there shouldn't be any splices. Your temperature sender wire (for your dash gauge) also runs through that area, but I am unaware of a splice in that wire. The other wire that it could be, is there is supposed to be a purge canister valve there. Looking at your PCV valve, there should be 3 hoses, 2 big, 1 little. The one big one goes to your crankcase (connects into a breather under the intake), the other big one snakes around a vacuum tap in the intake and connects into your EGR emissions spacer below the carburetor. The third and smallest line should come straight up out of the valve and go into the purge canister valve. Following that line from the other side of the valve would take you down to your charcoal canister on the right frame rail. There is also a connection in that line that leads to your fuel bowl vent. All that said, that would be the only electrical connections in that area. As for your thermactor air injection system, that hose coming from the pump would go to a diverter valve. That valve is controlled by vacuum signals from solenoids located behind your coolant overflow tank, under the MAP sensor. The diverter valve would either dump air to the atmosphere, divert it to your exhaust manifold (look for a valve or capped off connection there) or down to your converter. (your line coming up from the converter, should have a check valve on the end of it). Not having it operational really won't hurt much except for emissions. What carburetor did I use? I backdated to the full setup from a 1980 Capri. It came with a Motorcraft 5200 (Basically a Weber DFEV) and Duraspark ignition. I used the Duraspark distributor, but instead of wiring in the Duraspark ignition box, I bought adapter harnesses and plugged the distributor directly into an MSD 6A box and plugged that directly into the already-existing EEC IV TFI coil. Makes for one powerful ignition and a good running carburetor. I plan on eventually putting an actual Weber DFEV on it. Should gain some HP (nominal, but worth it) and some fuel economy then.