As for Chrysler OEM keys, I believe there are differences in the head of the key, from year to year, either in shape or logos. BUT be sure to match the letter stamped into the shank to ensure that it matches what's now in the car and works. The letter defines the slots in the key blank, width and spacing, which matches the tangs in the key cylinder that allow the key to "fit" and slide into the cylinder. Plus whether the blank is for the doors, ignition switch, etc.
To me, matching the letter code would be the first thing I'd look to do. Then worry about the correct head style/shape for the model year of the car . . . verifying what you need from factory literature illustrations (hopefully) or prior knowledge.
In the realm of GM keys, each one has the letter code ID on them. Then each letter code blank can have several different heads on them. For example, a "H" door blank on a Chevy application would be the normal rounded head, but on a Buick "H" blank, that one had a large head that made it easier to hold and turn. Each one would work in the cylinder, just the different head size/style for the particular carline application. The 1957 Briggs&Stratton "A" blank could be replaced with a 1970s "A" blank, which is thinner, but still fits the "A" blank cylinder of '57 although the thicker "A" will not fit where the thinner later model "A" would fit, due to its shank thickness. Might need some trimming of the square head (the '70s key) to fit the '57 ignition cylinder, too.
To me, ALWAYS verify that a part is actually an unused, not installed, part BEFORE paying the premium price for it. Especially if you're chasing a date coded item or similar. NOS = OEM, NORS = Aftermarket Replacement Part, not factory, but sometimes better, depending upon the orig brand.
Always, do YOUR research. If you have any doubts, don't purchase until you're absolutely sure of what you need and are getting. And on "mail order" sites, ALWAYS read and understand their Return Policy BEFORE spending any money--period.
Many times, I tend to "over-shop" before making a purchase. But when I do, I'm confident in what I need and am getting. I might miss a few parts because of this additional scrutiny, but so be it.
Just some thoughts,
CBODY67