Where's the Rocker Pedestal on 1967 440 915 heads

My 67 383 needs a set of 440 915 heads, I've read when buying a set:
Measure
from the center of the rocker pedestal, to the deck.

Stock head should be in the 4.13-inch range. If it’s milled more than 0.60, leave it behind.

--- Where is the Center of the Rocker Pedestal, so I know how to measure correctly?