Excuse me for interrupting, but there is a new feature that I love and you might like.

Create a header and select it.
Click Insert > Header > Save Selection to Header gallery.
I would make a new Category here, something like 1Custom (so it will sort to the top), and give your header a name (perhaps a company name).
Delete the header from the page and make the next one, save it to the 1Custom category of the header gallery. Delete it from the page and make the next header, etc.
Save the template.
Now whenever someone makes a doc using the template, their Header gallery will have the custom choices available.