For whatever it's worth, the tubular overrider bars sometimes seen mostly on earlier TR6s were dealer-installed accessories and NOT factory equipment. That said, they can be quite useful in protecting your 6 from careless drivers.
Years ago, I had a 1970 GT6+ with both front and rear AMCO accessory overrider bars, and I (sadly) had opportunities to witness first hand how valuable they were. In one instance, I watched as the driver of a huge Chrysler sedan (this is the late 1970s, when those were about the size of aircraft carriers!) actually pushed my GT6 a foot or two during a feeble attempt to parallel park behind it! Since GT6s of that vintage did not have full rear bumpers otherwise, pretty much the entire rear valence -- and every lamp on the back of the car --- would've been trashed. /ubbthreads/images/graemlins/eek.gif