all longhorns have that line, yes. If you look on the other side of the bed in this photo, you'll also see where the stake pocket is back 6 inches.
All longhorns had wooden floors
All longhorns were 20 or 30 series, and 2 wheel drive.
No mention of it on the spid, other than the model number and wheel base.
Check out this real cool website;
http://www.longhorntrucks.freeservers.com/
(it's mine)