On the 71 and up B-Body cars, that valve that you gave the part number on is mounted on the right side of the engine compartment. Close to the firewall. I beleive it sits on a bracket.
However, that is not the valve assembly for a 69'
"B" body. The correct 70' and older heater/water valves are available either pricey NOS or there is a company rebuilds that valves. If you have one you can send it in and they will rebuild yours. I don't know the name of the company but if you google Dodge heater valve you should be able to find the company or maybe someone reading this thread may know.