There is a company that restores grills and trim parts that is out of Washington state I think. They bought up alot of the old "origonal" argent when it was going to be discontinued. They only use the paint on the products that they sell. So, short of shipping the car from one coast to another and having them spray the tailpanel with the correct stuff, I'll have to come up with something that's close.
I carried my argent samples around with me at the Nat's this year and compared the samples to an origonal 72 Challenger Rallye. The light argent was way too light. The dark argent that is available from Totally Auto was too dark. My sample that was a combination of both the light and the dark argent was very close. It was just a little too light still. My painter is going to try and darken up a sample just a little.
One of the things that I found out about the 72-74 tailpanel(that is often overlooked)is that the factory sprayed the entire tail light housing with organisol black first, before spraying the argent. If you look at an origonal taillight housing you will see small black specs showing through the argent. That is the organisol black that was applied first.
The center section between the light housings wouldn't show this effect because it wasn't painted black first.
When I have an argent sample that I'm happy with, I'll post it. I'm never going to get it to look 100% but I would like to get it as close as possible. Maybe 95%