Will this work?

Excellent! This is why this is simply the best site for technical help, thank you so far, so to answer a couple questions I am not using any of the trucks factory wiring this is simply a body sitting on a 81 Dodge truck frame, I might use the factory ammeter only because I am using the factory gauges IF I can to keep a factory look I am using a brand new ignition switch but it is a after market Chrysler switch with a Chrysler key even and it dose have ign 1 and ign 2, the MSD box has a green tach wire which is where I was planning g on getting my tach supply from the box is a 6200. I attached a couple photos.

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Now I know why you didn't post which MSD it was. LOL
That's probably 1980s era. Autotronics was the original manufacturer. Let me see if any of the stuff I have has that part number. Most of my stuff only goes back to 1989-90.