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Here is an interesting idea if you do heat the pistons with your rose bud torch. Know that the heat will transfer all the way through those Aluminum pistons 10 times faster than heat moving through that cast iron block.
Aluminum Conducts heat very well. So if you take a little time heating each one of those pistons they should come free for you. As you saw in the video they sprayed the penetrating oil into the cylinder wall gap when they were good and hot.
When the pistons cooled they easily turned the crank with the breaker bar.
That heat on the piston tops will transfer all the way down to the piston skirts, take your time they will heat up.
Don't want to dump too much heat too fast that it melts the piston tops, warm them up to temperature. Can check their temps with the infrared heat gun to know where you are at with the heat. Would guess 250° would do the trick, then hit them with the penetrating oil and let them cool.
Expansion and Contraction