[jhv48]

I ran 18/38 degrees advance on my 302ci engine with California 91 octane gas with no problems. Compression was also 10-1.

My last 427 sbf ran 16-36 degrees with 10.5-1 compression on 91 octane California pump gas. No problems there either.

Does your original setup ping when you use 91? If not, don't change anything and run it.