Not a lot of info. My F60L had it - it ran as far forward as the rear of the spring hangar, and from memory had another piece which ran just under the chassis rail, at right angles. They were very good for the propogation of rust.
As for uprating, that would be the normal assumption - they were used I think on many of the tippers as well... on the F60L I have a theory they were added when a winch was fitted. The F60L below was a winch truck and you can just see them there.
