"I suppose that I could justify a decision with the other two but that decision would never sit comfortably with me."
The examples are a bit black and white and the question should also include 'What would you do if ..", not that one necessarily knows how one will react in extreme circumstances.
Just for interest is there any "moral" difference between case 1 and case 3 ?
Perhaps it would depend on why those requiring organ donations needed them. If it was a case of self inflicted organ damage because of damaging lifestyle, diet or other abuse, would those recipients' "right to life" still over-rule the innocent healthy donor's life ?
What if the healthy donor agreed to commit suicide and donate the organs ? Could a recipient whose moral compass or religious belief regarded suicide as wrong, still accept the gift of the donor organ ?
Life is rarely black and white ...and the twin questions "Does the means justify the end ?" and "Is there such a thing as the lessor of two evils ?" are often just waiting to jump out at you and demand an answer.
That may be why so many religions (and governments) end up imposing fairly rigid rules.
PS What if the 5 on the track in case 1 had just killed 50 people in a terrorist attack and the single man was a railway worker ?
