Welcome II the crowd Radrider!Check out www.mustangii.org for a start on obtaining information. It should also provide some links to some parts suppliers.
Also, the King Cobra did not have it's own unique VIN, so it would be hard to tell the car just by looking at the VIN. But you are correct, 03 would indicate a 3-door hatchback, which is what a KC was. But, if you look on the buck tag (small metal tag usually found attached to the radiator support, visible just by looking through the front grille), and see a "KC" stamped on it, that's a pretty good indicator that it's a true King Cobra. One other thing that the impostors usually lack is the air ducts that run from the air dam to the front wheels, for brake cooling.
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Frank S.----MCA Member 40390
'99 Mustang coupe
'77 Ghia--"II Good"
'76 Cobra--project