During all the 428cj discussions IIRC it was Dennis K who mentioned the C8AX-C was the goal for the 427/390hp but it either wouldnt pass smog or drivability. So the good old 390gt/428cj cam was used instead.
C8AX-C is listed as "optional" for the 428CJ LOL but that was just to make it NHRA Stock legal.
Same grind is the stock 70-71 429CJ cam. A little rumpier than the 428CJ cam but liveable even in winter BTDT.
Per Muscle Parts it adds 13-15hp vs the 270-290 428CJ cam, and I believe that having run a couple of em.
C8AX-C is 220-230-116 at .050, Ken at Oregon used to like to grind about 220-230-112 for a little more kick. And a rougher idle.