I have a pre X coded 1969 camaro, and when I pulled the rear brake line out it was a one piece line. Then just recently I ordered a new brake line from "The right stuff" and it was a two piece line that required a brake "hold off valve". They said I could either order the one piece line or a two piece, and where both correct for '69. The brake hold off valve is located half way down the body. Supposedly this valve retains residual pressure for the rear so can anyone say why GM went to this and what other, if any other vehicles used it?