When you say "stripped", do you mean the actual threads or that you rounded off the heads? It sounds like you rounded off the heads... if so, I think a vise-grip might work to get them out. Use some kind of penetrating oil first as it seems they are stuck pretty good. As far as replacements go, there may be different types of metals for them (ask the guys at Advance). Just make sure the threads are the same as the stock ones if you get other than OEM.