Yes, you can switch over but only if the vehicle came with that as an option. Most diesel engine vehicles came with the hydralic system because the engine will not provide enough vacuum to operate the "normal" or vacuum brake booster. You will need to replace the hydralic unit with the vacuum booster and also the master cylinder. You can find a fitting on the intake manifold below the air intake to use as the vacuum source. Most often it is found toward the back of the engine. Some auto part stores sell the booster with a new master cylinder already attached. I would not use used parts due to safety reasons but you can if you want to take a chance.