Image of where I tapped the ignition wire in the Commodore - for the paedia
Sorry to start a new thread for this, in a bit of a hurry but want to post it before I forget.
I ran a new 30 amp ignition feed to the coil for HEI, and this is where I fed it in. It was not necessary to touch the ballast wire in this configuration, though its possible the previous owner did something funky there that I haven't yet found.
Dunno if the image is good enough to use, it's the only one that turned out even relatively non-blurry!