Also, dont forget that the word "GEOMETRY" in Valve Geometry implies more thinking is needed. If the height (y) was changed and horizontal distance stayed the same, the hypotenuse may change much more or less than you think. x^2 + y^2 = z^2 (z = pushrod length). Now I dont know all the numbers to put in, but if we look at a simplified example: say the initial y = 5, x = 3, z would be then 5.8. Now we increase the height by 2, to y = 7. Now, the z would be equal to 7.6.

This also only works if the angle between the height and the horizontal distance is 90deg (which I am not sure if it is). I am just trying to explain that there are more variables than you think.

So, depending on the stock head gasket thickness, the difference in head gasket thicknesses should be less than the difference in pushrod length (assuming the horizontal distance stays the same... which it should).