Part of the under dash harness goes through the firewall, on the engine side, the harness has a red wire it goes through the spark plug conduit and exits near the distributor it gets connected to the coil. Under the dash, the harness has a red wire that goes to one side of the ignition coil resistor, it is the only wire on that side of the resistor.
There is a heavy yellow wire at the start switch that goes to the ammeter and through it's cage on the rear, non stop it then goes to the fuse block and ends at one terminal. at the same terminal of the fuse block is a yellow black wire that goes to the ignition ON/OFF switch. The second terminal of the ON/OFF switch has a red wire that goes to the second side of the ignition resistor, at that terminal is a second black green wire that goes to the oil pressure gauge.
That is the ignition circuit.