My boat (#112) had the same problem. The bolts were seized into an aluminum plate under the mast step. I'm not sure you want to re-drill, as then you'll have to tap the aluminum again. Also, that's a lot of stainless to drill through.
Min ended up getting rebuilt. The steel into aluminum caused a good portion of the plate to corrode, so after the mast was off for about a month, the upward pressure from the increased volume of the aluminum oxide cracked the step. I ended up digging out the entire mast step, and having it replaced... No aluminum this time.
