[OrrieG]

I think you are missing the proportioning valve, the lines are two different sizes (larger for front discs, smaller for rear drums) and cannot be interchanged. If you have the brake lines connected directly to the master cylinder you do not have the ability to "Proportion" the pressure front to back. you also loose the ability for the front or rear to work independently if there is a failure. Depending on how the mc is mounted you might also need check valves in the lines to maintain pressure and keep one end from doing all the work.