The real life tracks or all tracks in GT5? You may be able to find information on the real tracks, but I'm not they've released dimensions for anything for the PD-created tracks.
I'm not sure if you could really use it with the relative suspension measurements. If you find the height of the curbs in inches, how does that relate to "-12" suspension?
I don't know how reasonable it'd be to have real world dimensions for tracks that are GT5 only. The easiest way to get that info might be to compare car height and just figure out the scale based on that (assuming the stock height of whatever car you pick is correct).