E-Body shafts only have 2 lengths (manual & power steering), but the difference in length is in the lower half. So I think they all get repaired to the same length. It's measured from the top of the threaded end to the first of the plastic pins. I could double check some un-collapsed shafts, but I think it's like 16 3/8" or around there.
Mopar sold a kit to repair the collapsed steering column shafts. It did not replace the pins, instead it glues the shafts together so they would still collapse if in an accident. So that might be a good option to try first. If I had a collapsed shaft I could play around and find a good glue that would hold up to about the same impact strength as the original plastic pins.
[img]http://forum.e-bodies.org/index.php?action=dlattach;topic=199.0;attach=1520;image[/img]