Top of Firewall Paint Line

[x33rs]

May not apply to your 67 but my 69Z is a 12D Norwood car and it doesn't appear to have been masked at the firewall. It's a black stripe car and it's clearly visible that they sprayed the gloss black under the cowl and just extended it all the way out the top of the firewall. Then a duller black transition can be seen on the forward facing firewall. My firewall blackout wasn't applied all that great either as there are areas of Frost Green showing through around the trans tunnel area and under the booster.

But that's 2 years later than what you're looking for.