but to answer your questions,
Audio sync
I use Media Player Classic because by using the + & - keys on your number pad you can resync audio - it just takes a while. I then use dvdlab pro to render a new ac3 without the delay using the audio delay tool. you could also use a tool called delaycut.exe - that does the same thing
alternatively you could use something like hypercube or besweet to dump the ac3 to wav (its only 2ch audio so that helps alot) but you could lose about 3db of volume with besweet and use something like vegas video* to normalise & sync it all up visually, then use besweet or vegas ac3 encoder or dvdlabpro with tmpgenc plugin to convert back to ac3..
*vegas video doesn't like Mpeg2 elementary video streams, use TMPGENC tools to mux video + no audio to get an mpg that vegas will open.
NTSC
In the PAL version I used convertfps=true - you dont actually need this really because the source is PAL ( I cant remember why I used it now - must have been a reason) take it out for NTSC (convertfps does frame blending rather than slowing down frame timings)
The Fps=25 tells directshow the framerate of the source - it needs to know this to playback correctly. Changing it to fps=23.976 doesn't 'break' anything but I prefer to leave it at 25 and use CCE to do the 23.97 itself because its doing the job anyway even when you use avisynth to do it... so..
directshowsource("D:\Home Projects\HTD\howard.the.duck.1920x1080p.dd2.0.ts", fps=25)
Crop(0,0,0,-8)
lanczos4resize(720,480)
ConverttoYUY2
Using CCE to change framerate
or
directshowsource("D:\Home Projects\HTD\howard.the.duck.1920x1080p.dd2.0.ts", fps=23.976)
Crop(0,0,0,-8)
lanczos4resize(720,480)
ConverttoYUY2
CCE receives correct frame rate but does it itself anyway
or even
directshowsource("D:\Home Projects\HTD\howard.the.duck.1920x1080p.dd2.0.ts", fps=25)
Crop(0,0,0,-8)
Assumefps(23.976)
lanczos4resize(720,480)
ConverttoYUY2
CCE receives correct frame rate but does it itself anyway
NTSC Audio
convert the audio (usually if your ac3 is 5.1 but 2.0 is ok too) with besweet - the belight frontend seems quite good - theres a setting to do 25000 to 23976 you do loose about 3db of volume doing this but its not that noticable by most people
or you could pitch the audio in vegas..
You should have enough to go on now, also, doom9 is your friend - as is the avisynth documentation