From memory, on a 289 head with an existing 53cc chamber, mill off .010" reduces the chamber volume by 1cc.
Check the specs on the compressed Reintz gasket. It may be thicker than the Fel-Pro compressed?
You will not know if the engine will ping on pump gas until you try it.
Actual measured 10.3:1 will run no problem here with 93 octane and iron heads.
Aluminum heads do not allow you to run higher c/r than iron though. It is the compressed pressure of the fuel that you are attempting to manage.
Aluminum and iron with the same compression ratio will create the same pressure compression to the fuel.
I wouldn't be surprised if you need to limit total advance to 32 and slow the curve down so that it is not in full until about 5,000 to 5,500 rpm?
Best of luck. Sometimes it's better to be lucky than good.
