Here's a quick and dirty method for extracting a b&w image from a 3D color comic.
In Photoshop 7 or later
1. Scan in color at whatever resolution you choose (300 ppi is recommended)
2. Open the scan in Photoshop and click on the [Channels] tab (next to the Layers tab)
3. Click on the icon for the Red channel (or the Blue channel) whichever looks better to you
4. Click [Image][Mode][Grayscale] and answer Yes to Discard Other Channels question
in Photoshop CS or later:
5. Click the half-white/half-black circle at the bottom of the Layers palette.
6. Choose Levels
7. Click the white eyedropper and click on the darkest white area in your image
8. Click the black eyedropper and click on the lightest black area in your image
(note: these take some trial and error to get the best results)
9. Click OK and you should have your 2D image.
(note: in pre-Photoshop CS, just substitute [Image][Adjustments][Levels] for steps 5 & 6)
Give it a try. Here's a link to a 30 second effort on a Harvey 3D Adventures #2 page. With more effort and time, I'm certain that one could do a lot better.
http://www.bpib.com/temp/3D-blue.jpgHope this helps.