No, a 351 pan will not fit a 302. A 351W uses a 3" main journal crank. The caps are much larger. The pan seals to the rear cap, so the U shape at the rear of the pan is larger.
That's a quick way to tell a 302 pan from a 351 pan at a swap meet. The U shaped areas on a 302 pan are the same size front and rear. The 351 has a smaller (same as a 302) U at the front and a larger one at the rear. It's the same size on the front because the pan seals to the timing chain cover at the front and the timing cover is the same size on both engines. It's an obvious size difference when seen side by side.