You get a diagram for a fan belt routing for a kenworth 300 1995?

That's dependent more upon the engine than the truck it's installed in. The T300 was available in configurations ranging from a single axle Class 5 truck up to a tandem axle Class 8 truck... I believe Cummins options ranged from the 5.9 liter 6BT up to the 11 liter M11, Cat had a similar range of engine options, and the 11.1 Detroit was also available.