How to deal with historic tar-balls

[nn6eumtr <nn6eumtr@gmail.com>]

I have a number of older projects that I want to bring into a git 
repository. They predate a lot of the popular scm systems, so they are 
primarily a collection of tarballs today.

I'm fairly new to git so I have a couple questions related to this:

- What is the best approach for bringing them in? Do I just create a 
repository, then unpack the files, commit them, clean out the directory 
unpack the next tarball, and repeat until everything is loaded?

- Do I need to pay special attention to files that are renamed/removed 
from version to version?

- If the timestamps change on a file but the actual content does not, 
will git treat it as a non-change once it realizes the content hasn't 
changed?

- Last, if after loading the repository I find another version of the 
files that predates those I've loaded, or are intermediate between two 
commits I've already loaded, is there a way to go say that commit B is 
actually the ancestor of commit C? (i.e. a->c becomes a->b->c if you 
were to visualize the commit timeline or do diffs) Or do I just reload 
the tarballs in order to achieve this?

All replies appreciated!