What spark plugs does a 350 Chevy use?

What is the correct spark plug gap?

between 0.020 and 0.040

Are 305 and 350 spark plugs the same?

The 350 and 305 are identical looking.2011-02-19

What happens if the gap is too big on a spark plug?

The Spark-Plug Gap However, if the spark plug gap is too large, the spark is unlikely to consistently "jump" across the long distance between electrodes, thus leading to a rough-running engine or one that doesn't run at all.2017-03-27