Help with digital video and DVDs

So I'm trying to burn all sorts of movies and TV shows to DVDs with professional looking menus and such, but I'm running into a few problems. I'm not very experienced in this field, but on the other hand, I'm not a total n00b either. I would probably understand most terminology you through at me, but my practical experience in this area is limited. I thought I would devote this thread to getting help on various issues I may come across throughout this project.

The first:
I downloaded Howl's Moving Castle in a matroska container, and used VirtualDubMod to split it into the DivX avi, mp3 audio, and subs. The movie is 640x352 (aspect ratio of 20:11).

So I have a menu created in Adobe Encore, and it's all ready to have the avi file imported into the timeline. However, Encore won't let me import it unless it has a resolution of 720x480, 720x486, or 704x480 (I believe these are the standard resolutions for NTSC DVD). Now, I could just put the video into Premiere or a similiar program and resize it, but some issues arise. Wouldn't the aspect ratio or pixel aspect ratio be changed without relation to the original widescreen input ratio? Encore won't accept a ratio of 20:11, so I'm thinking my video would lose it's original aspect ratio. Also, I would lose quality by conveting it. As you can see, I would like to avoid doing any kind of re-encoding/conversion. Any suggestions?

Jam it back in, in the dark.

*Bump*

There's nowhere I can't reach.

*Bump*

This thing is sticky, and I don't like it. I don't appreciate it.