I checked your conversion to PAL resolution, and it keeps it close enough to the correct dimensions. It may not run as quickly though, since everying before the resize is MOD2. You might try:

orig=Crop(0,120,0,-120,align=true)
...
Spline36Resize(720,448)
...
AddBorders(6,64,6,64)

I'll check all the pages you posted for the plugins and verify against mine tonight when I get home. In the mean time, make sure you have Removedirt from here: http://home.arcor.de/kassandro/RemoveDirt/RemoveDirt.htm
and Removegrain from here:
http://home.pages.at/kassandro/RemoveGrain/

-G