You can edit the HTML File, and insert an anchor at the point you want reading to start.
Notepad++ or KompoZer are good freebies for editing HTML.
With MobiPocket Creator you than can rebuild the book.
I created some eBooks from scratch using Project Gutenberg's HTML-Versions, they look very nice on my Kindle

I stripped the License Bla Bla however, so I think I cannot upload my versions here.