If it don't say 340 cast only then its a 360. either way it's NOT for a forged crank. Aka internal balanced.
Man no wonder you got this 340 for a song. .....vibrates, like a MO FO, over reved it and now it has a miss due to leaking bent valves.........
You might want to roll them push rod on a flat surface and see if you have any bent ones.