JUST A GENERAL PAINT MATCHING QUESTION

DD-1 is a metallic color, as are ALL of the 1967 Plymouth colors with the word "poly" in the name. 1967 DD-1 is "Light Blue Poly", a silvery-blue metallic. I had a Barracuda convertible that was DD-1. I can't speak to the current color of your car, if it has been repainted.
That, of courrse is the BIG QUESTION!!!
Has it been repainted???

Having to dig around in the door jam corners and crusty bottom corners through several layers, I suspect this may be the case.

Thanks again to BrianT for the O'Reillys reminder.
They do not use the Spectrum" system any more here, per se.
But, they do use the camera.
I spent a good 2 hours there today, including a lunch wait for Ray, the paint expert.
(The new guys couldn't even find the old paint info in their color system)
His first try was closer than anything I had tried so far, and he put it in rattle cans.

The second try was flipping the metallic with another ingredient number and he came relly, really close.
I bought both cans, since I can always use first color in the trunk. He gave me a discount for the first "off" can.
Now that I've got the custom formula, I can pass it along to the guys who will paint my engine bay; unless they just want me to get a gallon from O'Reillys for them.