I spoke too soon about the alternator idiot light LED. I had the LED wired in parallell with the alternator wire through the relay I was using to troubleshoot. The relay coil provided enough resistance for the LED to light. No biggy, I'll just try adding a 100 ohm resistor in place of the relay. So it'll be wired: +12V ignition to resistor and LED +, resistor to alternator D+ and LED-.
Moving the thermocouple extensions from the left side of the car where all the other wires are to the right side and tucking the CHT probe under the shroud as far away from the spark plug wires fixed the noise problem.
So, now I only a few loose wires. Nothing I haven't lived with for years.
