I thought about inserts - I'll have to see what material is available. In addition, it may be possible to simply drill two new holes in the existing gudgeon and drill and tap new holes into the backing plate, leaving the gudgeon in the same position. Not as desireable as using the same holes, but worth a thought. The machinist here at work suggested using a pre-drilled block to guide left-handed drill bits (going from smaller to larger sizes) to drill out the bolts. He said that occasionally the left handed drills will catch in the bolt, and will be turning in the right direction to back the bolt out. The vibration from drilling into the bolt might loosen some of the corrosion, and make taking out the bolt possible, he says. He also added that he only felt that I "might" be able to drill out the bolts. I ordered some left handed bits today - should be here tomorrow. We'll see..............