On that note if he wants a relay, I'd cut the switched IGN1 coming out of the bulkhead, use the bulkhead end to key a relay, and put the other end on the load contacts.
On a '70 Dart the dark blue wire comes from the bulkhead, runs to a factory splice who's branches form the blue field wire between the alternator and the regulator and one also runs through the ballast resistor and then to the coil forming the run wire for the ignition.
I want to make sure I understand your instructions. I freely admit that I'm kind of thick and like things spelled out.
Cut the blue wire between the bulkhead and the splice.
Use the end coming from the bulkhead (from the ignition switch) only as the power source to trigger a relay.
Run a new power wire from a battery source such as the starter relay lug from the battery to the relay.
Connect the other end of the previously cut blue wire coming from the factory splice to the other side of the relay and use that new battery power source through the relay for the ignition run, field wire, and electric choke.
This being to reduce the current through the bulkhead and give a more steady/even flow to the regulator.
