Can I set a global header for all AJAX requests?

I did some additional tests and the code you posted works perfectly. If you have problems with something in how the parameters are setup, you could always to go the beforeSend call and modify the xml request yourself.

$.ajaxSetup({
    beforeSend: function (xhr)
    {
       xhr.setRequestHeader("Accept","application/vvv.website+json;version=1");
       xhr.setRequestHeader("Authorization","Token token=\"FuHCLyY46\"");        
    }
});