// get text of heading
var plansBlockHeading = $('.first .sub .one h4').text();

// filter to last 2 chars
var sup = plansBlockHeading.substr(plansBlockHeading.length-2);

// Wrap in a <sup></sup>
$(sup).wrap("<sup />");

$('.first .sub .one h4').html(function(i, html) {
       // make sure there's no whitespace issues
    html = $.trim(html);
    return html.slice(0, -2) + "<sup>" + html.slice(-2) + "</sup>";
});

var text = $('.first .sub .one h4').text();
text = text.replace(/^(.*)(.{2,2})$/, "$1<sup>$2</sup>");
$('.first .sub .one h4').html(text);

var elem = $('.first .sub .one h4'),
    text = elem.text(),
    html = text.slice(0,-2) + '<sup>' + text.slice(-2) + '</sup>';
elem.html(html);​