You can change the 30 small ring to a 24. If you have a long cage der. you should be ok with a 12-28, a 13-28 would be better.
You could also switch the front rings to a 48-39-24. The 13 rear and 48 front would give you a 100 inch top gear.
You can use this site to figure out what you need.
http://www.jbarrm.com/cycal/cycal.html