Yet another variation on the '67 Shelby's - they seem to be never ending.
This is in regards to the Nose Support/License Plate Bracket, a Shelby specific part that had some changes over the production run.
There were two gauges of steel used the earlier version(s) where heavier gauge (don't have that gauge difference handy at the moment).
The two more easily seen differences are the vertical end plates, early cars had holes in them and the later (majority) did not.
The second visual difference is the style of the license plate bracket that is welded to the support bracket. Very early have two support brackets jutting forward to the actual bracket the license plate attaches to. There is a drawing dated 10 12-66. Later about a month (11-12-66), this bracket became a one-piece plate with a 90 degree bend to attach the license plate to.
The repro versions available are typically the thinner gauge material, without the holes in the end plates and the solid license plate bracket.