Critical,
Each model has it own numbering.
427's are up to around 690 maybe into the 700's now.
289's models had a 4 digit code
GT's have their own sequencing.
By the time they built your particular car they had become very good at their craft. I have seen car #3 in person and it was fantastic after 20+ years. Your I am sure is that much better.
Enjoy!