What is the routing for a serpentine belt for a 1987 GMC van with a 5.7 liter ac PS and air pump?

There is generally a picture on the cardboard on the new belt. There is also a diagram on the label in the engine compartment under the hood. When installing the belt it is very intuitive except that you have to use a breaker bar and a socket to rotate the tensioner (smaller pulley to the left of the starter on the top row) counter-clockwise. This released the tension for removal and installation. Be sure and release the tensioner slowly so you don't damage it. When you route the new belt it must completely engage the grooves in the pulleys.