Mopar engines always overstated compression ratios, it is hard to get them much past their advertised ratios. Even the closed chamber heads are around 84cc unless they are milled excessively. To get a 440 to 12:1 means a total of 82cc above the piston. A steel shim head gasket is around 5, valve reliefs are another 5, so that means you have a zero deck piston with a 72cc head. Or an 84cc head with a dome that displaces 12cc. 10.7:1 would be the top of my guess range.
