Removing The Groove From A Track:

Actually, we're just going to move it out of sight. But it's just as effective. Before converting a Nascar3 or Legends track you need to get rid of the groove, because of the fact that in ICR2 it will look very ugly indeed.
[you will need 3doEd]
First open the <track>.3do in 3doEd. Look at the track and find the groove (make sure the display is Polygons) Double click the groove and hit "Edit Polygon". Look and see what the number of that color is and then close that box.
Now go to the top and click display again. Choose "Color Filter" and the number of the groove should already be filled in for you. Now check "Display Only This Color" and then change display to "Wireframe".
Now if you're lucky you should see only the groove on the screen. There might be a couple of other things that have that same color though. If those things are the lines around the track, fences or indeed any type of untextured surface, select "Textures Only" from the "View" menu to remove them from the view. If there are objects around the track that have the groove color assigned you can turn objects off by going into the "Object Filter" and checking "All Off".
Now zoom out until the entire groove will fit inside your square cursor. Double click and choose "Edit Point". Type in -10000000 for the Z coordinates, check "Update All Found Points" and press OK.
Now click "File" -> "Update 3Do File" and your file is fixed.
Thanks go out to Dave Noonan for 3doEd and RearViewMirror for his advice on this subject.