Here is some in from the 68 MPC.
Looks like for 67 & 68 there were four variations of the engine rear support cross member, part numbers C7ZZ-6A023-A, -B, -C, and -D.
The version I have is a bit early for the 428 CJ, not a lot of CJ parts listed, only a few. I did not look at 69 or later parts in other MPCs.
It is interesting that the 6 cylinder and 289 version moved from -C to -D for 1968, but the 302 lists the -C.
The 390 parts appear to be different for auto vs. manual trans, where as 6 cylinder and small blocks share the same part.
I don't see a running change in 68, the MPC I have has updates up to June 68