Bob, my engine slopes down at the front of the engine (rear of the bus). I did this to get the proper driveshaft alignment.
I was told by an expert that I would have a severe problem with air locks in the cooling system and the rear cylinders would overheat. Indeed, in a truck, the engine has a slight slope with flywheel end down.
The issue is that there is a small hose that goes from the head to the top of the radiator. In a truck that hose is connected close to the front of the engine so that any air (some created from cavitation) trapped in the head would travel to the highest point in the head and out the hose to the radiator.
I simply connected the hose to the rear of the engine and called it good. Have not had a problem.
Jim