I am attempting to write a module that uses ajax requests to another page within zen cart. I would like to mark the page that is to serve the data as "Simple": that is, there will be no headers, footers, or additional characters added to the served page (save the XML, JSON).
Is there a setting within Zen Cart that would allow me to mark this page as "Simple"?
You'll want to create a separate .php script which returns just the data you want (without the extraneous information). Don't use the Zen Cart page infrastructure (i.e. don't put the module under includes/modules/pages, etc.) - just create a file for the purpose you need.