Electronic ignition for Slant 6

None of them. Pertronix is a bubble gum ignition.
Just get a Chrysler 1974 electronic distributor, Mopar ecu, Mopar Performance wire harness. Easy install. Bullet proof, reliable Chrysler ignition. Update to an electronic voltage regulator while you are at it. Added bonus: All the parts are readily available, on the road.

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If you go this road, your going to have to upgrade your charging system regardless of what anybody else says! I don't know what it is with these Mopar Idiots that give this bad advice and not knowing the consequences of doing so. I tell people and post this every time someone ask's your question, and all the time the stupid people that think they know everything can't comprehend ****! Pertronix II is the way to go, easy simple, and hidden & looks like stock. Good Luck
Read, study, learn! charging system overview