I have wondered the same for a long time, but it's nowhere listed in the main source of bed size information (
Bed Sizes), nor have I been able to turn it up anywhere else.
The
Casita 17'
Liberty (not Legacy) main bed is 82" long (per website), and I've always assumed the 16' Liberty was a bit shorter. And yes, apparently it's no longer being made, but there are plenty of used ones out there.
I'd like to know, too. If you have the answer, it would be great to cross post in the "Bed Sizes" thread.