The oil pressure sending unit on a 1987 305 Chevy small-block is located on the
passenger side of the engine block, near the
front. It's usually a relatively small unit with one or two wires connected to it. You'll likely find it near the distributor and oil filter, but slightly further forward towards the front of the engine. It screws into the engine block.
Because the exact location can vary slightly depending on the specific engine configuration, a visual inspection is the best way to be sure. Consult a repair manual or online diagrams specific to your 1987 305 Chevy engine for a more precise location.
