adding a wire for my electric choke.

I use a piggyback spade terminal and jump off the input side of the ballast resistor. It usually has the two dark blue wires, but disconnect both wires at the ballast resistor, turn the key to the run position, then poke in there with a test light to see which one has power... Then use that one to run the positive wire for the electric choke. I've been running them for decades that way with no problem...