Where do these belong..?

I would not think there would be any issues using o e on each bolt/screw/ stud as long as there is clearance enough for the washer.

Thought just hit me...

I'm the 67 FSM it shows them being used on the outer screws/studs only.

I wonder if the 2 inner "lock" the manifold in place and the outer ones with washers allow the manifold to "slide" a little due to expansion?