Right along that bottom edge is the gap. I can rock it so one side is tight and of course it opens up more on the other. All three stock manifolds do the same. Heads do not look like they’ve been cut but the deck has, do S/S racers angle cut the deck?
A lot of SS Hemi heads have the intake face cut more vertical to reduce the port CC volume. The rules are you cannot cut into the valve cover bolt holes, so they angle mill the intake faces on the heads more on the deck side to avoid cutting into the v/c bolt holes. A photo of what you have should explain things better. I have an old set of SS heads and they came with wedge shaped spacers to fill the gap. You can see the gap to the china wall at the deck surface in the attached photo on a "Walcott" engine.
