Today i tightening up the last bolt on my centerbolt valve cover on my L98 and the friggin bolt busted inside the head at the threads. I can't grap it with vicegrips or anything because it broke halfway down into the head. Any suggestions?

Use an Easy-Out. Start by using a LH drill bit and drill out a recess for the "easy" to grab the bolt. If you get lucky, the LH drill bit will go ahead and bring it out. Use a shop vac while drilling to help control the chips.