One thing you have to remember, disk brakes are not self energizing like the Bendix style drum brakes your truck comes with. That will lead to more pedal effort without a booster. Small, lightweight cars, like early style hot rods and small sports cars can get away with it better that heavier cars and trucks. Even with the manual brake specific master cylinder, the pedal effort is much higher than it is for manual drums. Best bet is if you're going to swap to disk, go ahead and do the power conversion as well. There's plenty of vacuum boosters on the market for a stock location mounting.
