The Stovebolt Site Forums The Parking Lot Big Bolts Under floor master cylinder for 1.5 tons

I would look into a hydroboost set up that will use the power steering pump for added boost, then the correct master cylinder for the hydroboost your using. You should be able to mount it under the floor on your bus. It will help if you can determine what the bus will weigh so you can size things to handle your load.