Once upon a time I had this written down from when my Stage-6 heads were new.
If I remember right they were 89-cc`s new?

The 1997 catalog says "approximately 78cc".

I've heard of quite a wide variance beyond that, though.

I think they made them with both.
Mine were supposed to be 78 and when I checked them the inner 2 chambers were quite a bit different from the outer 2.
This was on heads I bought in 95.
I complained to Chrysler and they sent me a check after I had ICH equalize the chambers, mill to 78 ccs, set the stem heights, and valve job. The check was dated 3-21-97.
Back then they knew they had a problem and made good on it.
I have been running them since and have had no problems. Don

Pretty sure mine are 78. But they have been worked not sure what they are out of the box. I was also told they could be all over the place.