Where is the oil sending unit on a 1999 dodge 1500 318?

The oil pressure sending unit on a 1999 Dodge Ram 1500 with a 318 engine is located on the passenger side (right side) of the engine block, near the front. It's a relatively small unit and usually has one or two wires connected to it. You'll likely need to look closely to spot it amongst other components. It's generally threaded into the engine block.