I just picked up a 68 with a similar situation. I have not inspected it that closely yet, but I assume it’s an older repaint (at least the tailgate), as I suspect with yours. That’s where I put my money. I just think it’s more likely the tailgate was damaged and repainted long ago, rather than a factory miss.
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I live in California, but identify as a Texan
"If a job's worth doing, it's worth doing well"
Survivor "
Lil’ Mint" (67 c10 40k mile light green original paint)
Project "
C10 Fever" (68 factory black 396 swb)
Project "
Little Sister" (70 c10 blue original paint refresh)
Project "
Blue Bomb" (70 c30 blue original paint refresh)
SOLD
Project "
Vitamin C" (71 c10 orange original paint refresh)
SOLD