Add a custom variable to your google analytics data with the rank of the result leading into your page.

Get Google rank

if (document.referrer != undefined) {
	var rank 		= 0;
	var array = document.referrer.split('&');			
	for (value in array) {
		if (array[value].indexOf('cd') != -1) {
			rank = array[value].replace('cd=', '');
		}
	}			
	if (rank > 0) {
		_gaq.push([
		  	'_setCustomVar', 2,		// This custom var is set to slot #2
		    	'Google_Ranking',		// Variable name
		    	rank,				// Value to register
		    	2				// Sets the scope to page-level.
		]);
	}
}

/**
 *
 * Usage example
 *
 **/

<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'GOOGLE_ANALYTICS_SITE_IDENTIFIER']);
_gaq.push(['_trackPageview']);
		
if (document.referrer != undefined) {
    var rank 		= 0;
    var array = document.referrer.split('&');			
    for (value in array) {
    	if (array[value].indexOf('cd') != -1) {
    		rank = array[value].replace('cd=', '');
    	}
    }			
    if (rank > 0) {
    	_gaq.push([
    		'_setCustomVar', 2,		// This custom var is set to slot #2
    		'Google_Ranking',		// Variable name
    		rank,				// Value to register
    		2				// Sets the scope to page-level.
    	]);
    }
}
		
(function() {
	var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
	ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
	var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>