Engine driven hydraulic systems are actually more expensive than a pump mounted outside the vehicle on the plow frame or front body frame because they are more involved in attaching to the engine and running hoses to the blade actuators. Almost any plow company that sells hydraulic plows with an engine driven pump will have application charts and instructions on how to install one. I prefer Western brand or Snow-Boss myself.
http://www.thefosterfamily.org/snowplow/#mount