DBP,
Here's my latest attempt, using your cleaner, 449x720 jpeg.; it does look a little better than the last one, but I believe the muddy results we getting are because we're trying to improve and enlarge a small resolution image, up to an 8.5x11 or larger vector....if we could get the image in a larger format (preferably the actual size scan), I think it would be a better result.
http://www.mediafire.com/view/?vxjdfnu4p4vim2w
I'm using a program called Vector Magic, and it's always worked very well for me in the past; the results depend, of course, on the source image.
Rob