You could try buying a tap (same size as the bolt) and tapping the hole out depending on how bad it is. I Had that happen when I put my udp on I killed 2 bolts before I bout a 6$ tap and it fixed it in a heart beat. If you do go this way just make sure you take it easy on the tap, have you have every tryed to drill one out once you've broken it it is HARD!

If all failes for you text miller import they have everything for 2gnt's and at great prices plus very fast shipping.