The sledge hammer 'technique' requires the finesse that Steve has. Unless you are as deft as him with a BFH ,I suggest frequent applications of PB Blaster or Kroil over several days and much patience and tapping with a smaller BFH. When the corrosion has finally been dissolved ,it will separate without huge impacts.
Once you get a little movement in the joint ,tap it back together again,then apart.Rinse(with PB) and repeat - many times.
Some suggest heating it. That seems to help. I suspect it works because the heat helps 'draw' the penetrant into the corrosion and the expansion may help also. Be careful PB and Kroil burn eventually in a naked flame..
At work they use a "Bolt Buster" device similar to this because of a stubborn car(like yours) being immobile and hogging valuable lift space.
https://www.amazon.com/Bolt-Buster-BB2-ACC-Handheld-Induction/dp/B00ATSL7VE
https://www.youtube.com/watch?v=dAeFvUqTnk0
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