Membership options: radio not dropdown

I saw this topic: http://www.s2member.com/forums/topic/drop-down-list-for-payment-options/ and am wondering where I would go if I wanted to create radio buttons instead of a dropdown for different membership options? I am using S2Member Pro with PayPal Pro, and want to list all membership levels/options with one form on the membership options page, but I don’t want people to have to click a dropdown to see what is available. If you could give detailed instruction on what I need to change and where that would be greatly appreciated. Thanks!