My 455's were the 55 HP and were underpowered, too low tip speed, "4WD" sucked, etc.
The big thing the 580's have is not being naturally aspirated.
Always wanted one, never could justify it.
“Every step we take towards making the State the Caretaker of our lives,
by that much we move toward making the State our Master.”
~Dwight D. Eisenhower