Anybody now what the recommended maximum allowable DYNAMIC compression ratio is for 87,89,and 91 octane unleaded pump gasoline, for an iron head engine with .040 quench under towing load scenarios?

KB's site suggests no more than an 8:1 dynamic CR under the best (light load?) conditions without getting exotic. They also indicate a static CR of no more than 8.5:1 for an engine used for towing that is running on regular unleaded gasoline. I do not find how much more CR can be run with higher than 87 octane pump gas.

I can drop my dynamic CR by running a cam with a later intake valve closing, or I can choose a 28cc dish top piston that will drop my static CR to 8.8 - which seems low to me. I could also drop a cc or two out of my 64cc heads and stick with an 18cc D-cup piston for a static CR of about 9.5:1 but would 89 or 91 octane keep me out of detonation?