In 1.3, if you want to skip the main header altogether, and replace it with something else for ALL pages on your site, you have 2 options:

1. edit the includes/templates/YOURTEMPLATE/common/tpl_header.php
and replace its contents with your custom content

or

2. edit includes/templates/YOURTEMPLATE/common/tpl_main_page.php
and change line 47:
PHP Code:
  $header_template 'tpl_header.php'
to point to an alternate file located in your template's "common" folder (same place where tpl_header.php and tpl_main_page.php for your template are located)