Choose header content from entity-reference dropdown? Been struggling with this for a while... I know there is probably a fairly easy way to accomplish it but I haven't been able to figure it out.

The goal:
When a user creates a new page for the site, I would like them to be able to choose from several different headers using a drop-down list. I know I can set up blocks for the different headers and use the built-in functionality to have them appear on different content types or pages, but for various reasons I would like to have the header as a custom field within the page content type.

I have created a "Header Content" content type and used the Entity Reference module to populate a select list field in the page content type. I can display the selected option or the rendered entity it refers to in the body of my page without any trouble.

What I can't figure out is how to display the rendered entity in the header section instead of the main content. 

Put another way: When creating a new page or editing an existing one, the user should be able to select existing nodes from a drop-down list (this part is done). The selected node should show up in the header region (this part is giving me trouble).

I think it could be accomplished in one of two ways:

1) Using Views:
I tried creating a views block to read either the reference or rendered content from the parent page and display it in the header (or wherever I place the block) but I can't seem to get the relationship right.

2) Using a custom module
This seems pretty straightforward but I'm not sure how to reference the value of "field_header" (the name of my custom field using hooks. I'm also not sure if the data will be available if I configure field_header not to display in the configuration.

This seems like a problem that's likely to be solved already. Maybe I'm not phrasing it correctly when I search because I haven't been able to find any examples to help me solve it.
What I'm 99% sure you want is the Header Image module. It works by being able to select a piece of (node) content to place in some region thats been pre-defined.

Eg, put an image in some header region of your site. Or text or whatever ....