Need Mach 460 Expert to assist with advice or knowledge *PICS*

I've taken (in the process of) out the head unit and CD slave out of my 1995 Mustang Cobra. I purchased a Ford Mach 460 Stock CD head unit which was removed from a Ford Lightning.
I removed my CD slave unit and the the stock tape player head unit. I reinstalled the CD head unit out of the lightning. If I turned the volume up all the way I could then barely her the music. I tried leaving one of the plugs out in the back of the CD head unit do to it had a plug in it when I recieved it. Then I got nothing at all.
I finally got it to work but I had to have one of the plugs plugged back into the CD slave unit (left the power plug out) and I got the system to work.
Is there something I need to do to make this setup work with just the CD head unit to work on its own?

Stock system
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CD head unit from Lightning Truch(MACH 460View attachment 319409
CD head unit Ford part # if it helps
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This was the only way to get it to fully work. Thats just a speaker plug attached to the CD SLAVE unit it has no power, but system worked!
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SOME PLEASE HELP AND GIVE ME AN EASY SOLUTION.
pure vnm

I think I figured it out. I'm at work doing research on my dilema.
I removed the pictured below plug from the lightning Mach CD head unit even before I started taking out my original system. I will put this "CD slave delete plug" back in and try it. If it fixes the problem, I'll feel really embarrassed for these two post.