Been restoring car's for over 25 years, have used them all at some point in time, here is what you have to remember when dealing with any automotive paint. Yes its true in the late 60's and earlie 70's ppg was the supplier to mother mopar however this paint was shipped in by the train car load, So any given color has about 4-5 different shades to it even when original and untouched.
No fast forward 40 years.. Enviromentalist and the EPA ect.. The tints are the key to any paint match and the trouble is the tints that every paint manufacturer used 40 years ago has been outlawed.
Single stage enamals such as ppg's delstar, Dupont's Centari, ect are not even alialable in some places in todays world. Now the have Urathane Enamal's that replace them. here again all different tints, Some colors are close and some colors are way off the charts as far as a match of any sort..
Get into the newer Base coat /Clear coat paints and now the new waterborn paints and it gets worse in most cases because these are all new tints that were not even around when these car's were built.. Most if not all the major paint companies have done a pretty good job reformulating the original formula's into the new formula's with the newer paints but the holy grail of a direct match to a 40 year old factory color is almost non exsistant..What you need is a good paint mix guy with a real good eye that understands how to tint it to the proper color, and keep in mind he may have to go out side the color formula to do it so document what is put into it to tint it...
Just an opinion.....