Magnum wiring help

You need both the O2 and speed sensors, for the factory computer

"Evap system"? There is none in your car so I'm confused. What are you doing for fuel/ pump/ regulator? The original 67 tank is vented by a separate tube in the filler tube. That should not change, so vent is OK

The Evap from the mag tank is notan issue. The original mag fuel system should be single line, with the regulator at the tank/ pump

Wiring? You need to find the factory manual FOR THAT YEAR. It is frustrating, that more guys have not posted modded wiring on the net so "we" can find it LOL