Nothing wrong with having the early 65-67 calipers on a '68.
I ran my original 66 GT calipers on my '68 for years.
Interference of the earlier caliper with the Cragar SS wheels
surprises me too. Seems like I've seen those two together
ex-Global West GM
As the drill sergeant said, "I taught you everything you know. I didn't teach you everything I know."
"Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so."
- Douglas Adams