I wonder whether there is a retired Chrysler employee who saved a dyno room graph that plotted the Octane rating of pump gasoline versus the Compression Ratio of a test engine, hopefully the 1992 Magnum 5.2 V8?
Octane could be Research, or Motor, or EPA Anti Knock Index.
Compression Ratio could be either static, or the more predictive Dynamic.
I am not sure if Willem Weertman is alive or answering questions, but he was the chief engineer and he cared enough to write a book.
Since we are in the “Incredible Transition” to battery electric vehicles you would think secrecy about such cylinder head knowledge would have lessened to near nothing.