As said - here's the oil pressure sensor for 3126. Located next to ECM on filter side of engine.
The Silverleaf and ScanGauge get their readings from the ECM data, so there should be a "fault code" (engine check light) On if your oil pressure is out of specs. The dash gauge typically uses it's own sensor. But I believe you said the dash gauge and the Silverleaf are reading incorrectly (different sensors) - so I would definitely put a mechanical oil pressure gauge on the engine ASAP and confirm you have good pressure.