Figuring compression ratio ....

Great question. Depending on configuration , I have enough nitrous Equipment to deliver a 100-300 hp shot. Using the formula 2 degrees retard per 50 hp, A 300 shot would be 18 degree retard. A MSD 8680 dash controlled retard module has a IIRC has a 0-15. Degree .range. With a 200-300 shot cylinder pressure may be enough to cause head gasket sealing issues. The copper ..80 thou gasket is specifically designed for magnums. So...Im hoping to find a happy medium between dumping a lot of timing and/ or keeping compression lower.
Ideas ??
The heads in question end up 66cc after the chamber work to access the valve job.
66cc or less with milling is what you have to play with IF you decide to go with them.
Figure that in.