How low are 355 gears

Well there is a right answer in terms of final drive ratio in high gear with an automatic and 1:1 ain't it unless you have a lockup converter. It would be different if the torque converter wasn't in the equation. Since converters never completely lock up, you'll never acheive 1:1 in high gear because the converter is a fluid coupling and always has a percentage of slippage. Even more reason to try to keep RPM to a minumum if the car will be commuted a good distance one way.