I'm having some luck in testing with the following script. Feel free to critique; I'm new to all of this. I haven't actually converted a real video yet.

import("TempGaussMC_beta1.avs")

directshowsource("input.m2v")

# crop top and bottom from the 4:3 frame
crop(0,72,0,-72)

# stabilized deinterlace (also doubles frames, so we undo that with selecteven)
converttoyv12(interlaced=true)
tempgaussmc_beta1()
selecteven()
converttoyuy2()

# scale image 2x vertically, interpolating missing fields (slow)
eedi2()

# stretch to anamorphic ntsc frame
spline36resize(720,480)

# compensate for the blurring effect from all of this resizing
sharpen(0.25)

# interlace the video
bob(0.0, 1.0)

# set NTSC video framerate
assumefps("ntsc_video")

EDIT: Script fixes.