I'd just email the mfg and ask exactly how they measure their column. I can see how you are a bit confused though. I just looked up a Flaming River column on Ebay and it's listed as a 28 inch column but the total length is 33 inches ???????????????? say what?
I'm not sure what brand you are looking at but the Flaming River site makes it pretty simple
http://www.flamingriver.com/index.cf...=cat/cat80.htm
Other sites probably have similar how to order info posted.
If you aren't looking for a real fancy column I'm another who likes the 67/72 Column especially the ones that came with compound four speed trucks with no shift handle on them.