stock cast iron gt40 not p combustion chamber size?

[Danny's 94Cobra]

I am going to purchase a DSS bullet 308 but I would like to know what combustion chamber size these heads have on my 94 Cobra. DSS asked so that we can figure out the compression on the engine since I have a Vortech S trim we don't want to much compression. Any body know what is the most compression I can get away with my charger puts out about 12 psi.
Also what is the stock compression on my original motor? I would appreciate any input.

 

[TMC]

These are the stock heads that came on the car right?

Is so then they are 61-62cc.

 

[mackey]

DSS Bullet 308? Vortech S-trim? Why on earth are you running the GT40s still. I would change them out. Seems like you have enough money build on the engine. i would get the heads first and them have them figure it out with the new heads.