Well, shut my mouth.
That seems odd, seeing that some of the 402 CI engines made it into late Camaros; some even with the 3 character suffix. Same with rear axles: some got the C in front of the two two character suffix. Some of the "C"s were peened over on axles.
But, I am with Wilma. Will defer to the gurus.
A few years ago, this seller sure thought they were used on late 69 cars:
https://www.yenko.net/forum/showthread.php?p=1221356