Electronic Ign/Hei/Ballast Delete Wiring?
There are two wires that go from the bulkhead up toward the ballast that carry "Key on" ignition power.
One is hot only in the start position and one is hot only in the run position and the recommendation is to tie those two wires together and use them for the HEI coil supply. (Red wire on the grey connector.)
You may have to disconnect your starter at the relay and disconnect the coil positive wire to test light out these two wires.
Are you sure your ballast is wired like the pic shows?
You might have to leave the ballast in the regulator circuit and use the wire that comes of the coil positive as your ignition power.
The thing that concerns me is that the way it shows wired might put a damaging amount of power through your regulator if you tie those two from the bulkhead in your pic together and give the regulator a full 12v.