To find the volume of a beveled dish in the piston top you need to calculate the averaged volume of the major dish and minor dish volumes.
Measure the dish depth and the two dish diameters with a dial caliper and short straight edge. I can help ya with the math.
I've never seen a vortec head pull the pressed in rocker studs with 1.26" springs and .450" lift. Leave the rocker studs alone or just drill and roll pin them if you're going to loose sleep.