My problem using BD has always been I could never get satisfactory results when I start with a well coded (and elegant) .html ebook, namely most Project Gutenberg ebooks!
I solely convert from .html (with images) and have never been able to achieve good results using BD as others have done so easily when starting with text files as their source.
But, if your wish is to have Sony PRS-505 formatted ebooks from that or other Project Gutenberg ebooks, why not try my freeware
GuteBook (see the link in my sig below) to convert it for you (the way you like it).
I converted that PG Etext #6317 to my reader's .imp format as well as a Sony .epub and .lrf at the same time. I, however, did
rerun my ebook creation using the GuteBook supplied "rebuild-6317.bat" batch file to correct a minor issue, namely the captions below images didn't start on a new line underneath the images as expected, so I inserted a "<br />" before every caption in the source file "6317-h.htm".
To rerun that conversion for one ebook format just double-click that batch file. If you created more than one ebook formatted ebook i.e. .epub and .lrf, then you need to edit the "rebuild-6317.bat" file to insert "start /w " in front of each invocation of "ebook-convert" therein. This is necessary since after I created GuteBook, calibre now closes the ebook-convert DOS window when it's done and my batch file unexpectedly terminates early. This is the accepted work-around for this issue.
If you want I can upload my .epub or .lrf ebook creation here for you to see how it looks...