To pinpoint its location you'll need to consult a repair manual specific to your truck's engine. A Haynes or Chilton manual will have diagrams and detailed information. You can also often find diagrams online through sites like autozone.com or others that provide repair information for older vehicles. Searching for "[your engine size] 1995 Dodge Ram oil pressure sensor location" should yield helpful results.
Without knowing your specific engine size, giving a more precise location is impossible.