Compression Ratio w Vortec

[rcazwillis]

Need thoughts and experience.

1974 block with flat tops bored 60 over. Standard stroke. Was going to put the heads (883s I think) that came off it back on it. However, upon inspection valves are stuck in the guides. Don't know the extent yet, but they are 75cc chamber heads. Compression would be in the 8-8.5 based on calculators on line.

I have new vortec heads that will come off another engine that has dished pistons and an oil burning issue and will be replaced by this one. Vortec has 64cc chambers and will give 9.8 compression best I can tell. Research indicates the vortec has a better quench area and can handle 9.8 on 87 octane with correct timing.

I don't want to back timing off to nothing and I don't want to run 91 octane as it is Zane's daily driver. Am I going to get away with this or should I do replace pistons with dish to drop the compression?

Thoughts, experiences?