Quickie... stock 66 gas tank size?

When I ran out of gas in my 65 it only took 14 gallons to fill it back up same as the old falcons even though my owners manual says 16. Most after martket tanks are at least 16 gallons though. Since you never know for certain without running out of gas it might not be a bad idea to keep an extra gallon of gas in the trunk if your gadge is acting up. Always better safe then sorry.