Very little information is contained in the VIN of a U.S. sold '70 Nova. It will tell you if the car is a V/8 or a six, but not the actual size of either engine. It will also confirm the year of the car and the GM, plant where it was built. The last digits make up the production number of the car.
If you have a 1970 Nova that was shipped to Canada for new sale, you can contact Vintage Services Canada and they will supply (for a fee) complete build documentation for your VIN from GM Canada records.
The trim tag found on the firewall in the engine compartment will also give you information on things like original exterior color, interior color, etc. There is nothing in the VIN or on the trim tag to identify whether a '70 was an SS.
Yeah build and trim info is about all your going to get. All the older cars with the short 13 digit vin you will not find any owner history or accident history. I think it all changed around 1978, I may be off, when it went to the long vin. I believe 17 digits. You can get history on those.
Sorry, you can only tell if your car was a six or V8 by the VIN. The only way to tell size and HP of a V8 equipped vehicle is if the car has the original engine in it or if you have the original build sheet. The original engine will have the VIN and build date with engine code stamped on the passenger side cylinder deck.
The best places to look for build sheets in 3rd gen Novas are behind the upright back seat cushion and behind the side panels where the window cranks for the back side windows are. Sometimes folks have found them on top of the gas tank, but they're usually badly deteriorated after 50 years! Once in a great while, you'll see one taped up under the dash.
You can sometimes find 'partial' build sheets in the seat cushions, but those typically only contain information about the seats and other interior parts. The document that really gives the most information is called a "chassis broadcast sheet".
If you're able, post a few photos. The most helpful would be those of the cowl tag, the steering wheel and column and the floor shift (if so equipped). If the car is original, it would be helpful to know if it had front disc brakes or dual exhaust (tailpipes).