How to update the system generated fields such as Created, Created by, modified , modified by and Comments for list items

I am working on 5 team sub sites, each sub site have 2 issue tracking lists which are based on 2 different custom content types.

Now our customer asked us to merge these two issue tracking lists into one list, that contain all the items from the two lists. So for example if currently we have 10 items inside the first list and 5 items inside the second list, then the new list will have 15 items.

Now currently I have around 60 items that need to be transferred inside the new list, and I do not want to over-engineer the case . So I am planning to do the following steps:-

1. I will create a new list which represents the new list, without any items.
2. Then I will manually copy/paste the content from the current 2 lists into the new list.
3. I will hide the 2 old lists , so users will be adding /modifying the new list only

Now this should work and it might take around 2 hours to complete which sound valid. But I am trying to find a way how I can preserve the following values inside the new list items:-

1. Original created date.
2. Original modified date.
3. Original created by.
4. Original modified by.
5. Also the issue tracking list items  have comments inside it, and each comments have created date and created by which i need to preserve the original values of them.