The crankshaft position sensor (CKP sensor) on a 1995 Ford Aerostar is located on the
passenger side of the engine,
near the crankshaft pulley. It's usually mounted on the engine block itself, fairly close to the bell housing. You'll likely need to look underneath the van for the clearest view.
Because exact placement can vary slightly based on engine specifics (3.0L Vulcan or 4.0L Cologne V6), a visual inspection with a repair manual or online diagrams specific to your Aerostar's engine is highly recommended. A repair manual will provide the best and most accurate location.