Change authors of 500 subscribers without manually doing it

Hello,

My problem is that we manually uploaded a bunch of information from a previous map.

Now we want people to be able to edit and change their listing. They do not have a profile with our wordpress.

I know that I could manually create a profile for all 500 and then also tie that profile to the listing by marking them as author temporarily then switching back to subscriber. However, this will take a lot of time.

Is there a more expeditious route that anyone can think of?