This is a genuine GM Duramax Van Thermostat Housing. This is often a popular choice for many drag racers and sled pulling engine builds as it will allow for more clearance for custom coolant pipe configurations.
This forward facing thermostat housing will allow you to eliminate the cooling tube that crosses the drivers side valve cover. This rerouting opens up valuable under hood real estate and allows direct access to the injectors and valve cover.
This is an excellent addition to trucks with twin turbos and duel fuelers.