On a 4AC Sprinter the top rad hose goes to the head and the bottom radiator hose goes into the block. I dont see why it would be any different on a 4age.
Necros is right, the top hose goes from the head to the top of the radiator, and the bottom one goes from the waterpump (via remote thermostat is using FWD waterpump) to the bottom of the radiator.