var url = window.location.href;
var oldUrl = "http://oldurl.tumblr.com/";
var newUrl = "http://itsmemacleod.tumblr.com/";

// Split fucking Query strings
var splitString = oldUrl.substr(url.indexOf(oldUrl) + 1);


if (splitString.length > 1) {
   // New Url With Query strings
   newUrl = newUrl + splitString;
}
window.location.replace(newUrl)