[Tireiron]

You are correct, they are symmetrical side to side. The important one is between the heads and the intake manifold. Around an 8mm phenolic spacer should sit about right. The one between the upper and lower manifold doesn't matter if you keep the heat separated from the heads to the lower manifold. The intake manifold gasket from Subaru is almost dead on, I've never felt the need to port match a Subaru intake because of how close everything lines up.