Should we kill healthy people for their organs?

Well if your coming from a utilitaranistic view then yes, you can say you did the right thing.
This is no different from the train senario where on one track there is five people and on the second one person.

Do you pull the lever to change the trains direction and kill only one person?
Either way you go, its still murder.

For me I don't like to toy or mess with death, so not pulling the lever in my opinion saves you the guilt.