Ignition wires

I like connecting them together under the hood at the harness, and then the new ignition wire to those. (on the harness side using the brown and blue that used to go to the ballast.)
When I did mine I cut those two all the way back to the main harness, connected them together with my new ignition power wire (the red MSD on yours) and taped them back into the harness.

I don't know why Del had you do it under the dash, unless there was some reason for testing or something.
Under the hood is way easier, and also the way we have our HEI customers do it.

And just an FYI, if you wish you can trim all those wires that used to go to the Mopar ignition all the way back to the main harness on the firewall. (or just leave them and tie them back somewhere) either one.
Either way won't affect anything else at all as far as your new ignition is concerned.