How can you identify a 340 motor

Odds are very high it's a 318 with the odds being slightly lower that it's a 273. Buy a lottery ticket if it is actually a 340 since the odds are super low that it is a 340. Millions of 318s and 273s were cast compared to thousands of 340s. The can of racing fuel in the trunk is a decoy as any engine (even a 198/225 slant 6) can sip racing fuel.