Thanks, but it would be easier for me to replace the whole assembly. I might do that, if I can't get the Allen screws out.
Drill and replace.
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This should always be your last option. Common sense use of acetylene heat (torch) is always the way to go. I have not used the induction heat method but it is the new rave in heating ferrous metals. The problem with dissimilar metals (steel bolt and aluminum block) is the galvanic action (corrosion) that tends to occur between dissimilar metals that can bond the two metals together. You need to achieve expansion and contraction to break that bond.
So, what happened? Were you able to get them out or not?