1950 Ford Pickup truck master cylinder was replaced a corvette dual master and 7'' booster with 4 wheel drum brakes. There is a 10lb residual valve in the line to rear end then teed to each wheel. The front has the same a 10lb valve and teed to each wheel. Used a hand held vacuum pump and bleed the back with no problems. However the front is full of air on both wheels. I don,t see any leaks at any fittings and the only difference is front brake lines are about 5" or 6" above the master cylinder where they go over the frame and connect to flex line. Any body got fix for this. THANKS GOWSER.