Nick,
12-17. vehicle specific (124116)
This is the number I was referring to as the sequence number. This is the number everyone is using as a VIN when they don't want to post the entire number. The odd thing is that all the 2020 GT500's seem to start their sequence with 50. Is this the same thing your are seeing in the other 2020 Mustangs?
If that is the case, VIN 500115 could be a 4cyl Mustang, 500116 GT350, 500117 Mustang GT, 500118 GT500. Is this plausible?
100%. But that's how it's always been.
The last 6 digits are just a sequence. So if a 4-cylinder rolls through between two GT500s, they could be 506781, 506782, and 506783.
I have a 2020 GT getting built right now, and it's VIN is 1FA6P8CF4K5204316.