The new head looks pretty good, i don't see any problems with it from the picture.
One normally just measures the bore and stroke of the engine, then uses the measurements to calculate the volume of a cylinder, that yields the engine displacement then.
Measure the height (h) of the cylinder. Height is sometimes referred to as the length
Measure the radius (r) of the cylinder. Radius is the distance from the outer edge to the center of the circle. I simply measure the bore and then divide by half to get the radius.
Multiply the height by Pi. Square the radius. (Multiply the radius by itself) .
Multiply the product from Step 3 by the product of Step 4.
Write you answer in the proper cubic unit of measurement.