I doubt a 1970 engine in a station wagon has 4-bolt mains. Usually, the 4-bolt mains were used in the ultra (not that 300hp is not high performance in the day) high performance engines (i.e LT-1) and all truck engines.
The stock 350 CID engine in my 1971 RS Camero was a 2-bolt main that was rated at around 270 HP (I think). I ended up building my own LT-1 from the GM parts department and salvaged truck block and 2.02 angle plug heads.
