from your verbal desription, i would think this should work:
<?php if ( is_single() OR is_page('171') ) : ?>
<body class="last-page">
<?php else: ?>
<body>
<?php endif; ?>
from your verbal desription, i would think this should work:
<?php if ( is_single() OR is_page('171') ) : ?>
<body class="last-page">
<?php else: ?>
<body>
<?php endif; ?>