What piston is number one on 2.5L AMC engine?

On a 2.5L AMC engine (like the one found in Jeep CJ and some other vehicles), the number one piston is the piston on the front of the engine, on the driver's side. However, it's crucial to verify this with a shop manual specific to your engine's year and model. The flywheel/timing cover should also have markings to confirm. There can be slight variations depending on the exact application of the engine.