I would think what you're looking for would be as easy as using redirects.
Code:
<?php
$referring_page = $_SERVER['HTTP_REFERER'];
if( $referring_page == 'www.bcowwoutfitters.com'){
header("Location: http://www.bcowwoutfitters/index1.php");
}elseif ($referring_page == 'www.texaswaffles.com'){
header("Location: http://www.texaswaffles.com/index2.php");
}
Or use the simplest method, which would be to put each domin in it's own virtual domain on the server and save yourself the headaches of possible code breaks. (btw, my code has absolutely no error checking!)