To accurately locate them, you'll need a repair manual specific to that year and engine. A shop manual (like a Chilton's or Haynes) will show diagrams and pinpoint the exact locations. Looking at a diagram is crucial as simply searching visually on the engine could be difficult and you might miss some.
Searching online for "1985 Chevy Caprice 305 engine freeze plug location diagram" might also yield helpful images, but a dedicated repair manual is always the best resource for this kind of information.