I would say the top two holes should take the "Barracuda" script emblem.
The bottom two holes take either a "V-8" emblem that is rectangular, or the round "Formula S" badge depending on if it was a 318, 340, or 383 car.
318 got the rectangular "V-8" emblem, the 340 & 383 cars got the round "Formula S" badge. Since the two holes look like they are a little offset/crooked for the square badge, I would guess the Formula S badge.
What engine did it originally come with?
I have a red 68 Formula S in back that I can get pictures of in the morning.