I put a dual master onto my 55 1st series purely as a safety issue. If a line breaks or a wheel cylinder seal blows out on a single master system you stand to loose all braking power. On a dual system the front and back brakes are independent so if a line blows out you will only loose the front or the rear brakes but not both. Whether or not it is worth the extra $50 bucks is purely a personal issue of how important you believe that issue is (in my opinion) but you should also take into account how fast you plan to drive the truck, additional weight you put onto the truck, etc.... Hope this helps.
