A diagram for a Toro drive belt can be found on Toro's website. There are diagrams for drive belts found on Toro's models 74301, 74327 and 74353.
The diagrams can be found in a set of instructions for how to replace the mower belt. The diagrams vary depending on the model, and the year in which they were produced. Each shows the location of the mower belt, idler arm, outside pulley, spring, engine cover and belt cover. The diagrams for 74301 and 74327 also show the belt guide.
Manuals Lib has a diagram of a Toro 74568TE belt drive and the steps to replace it. There is also a detailed diagram of a Toro Riding Motor Tractor on Sears Parts Direct that shows the drive belt.