I currently have 4.56s and absolutely love them , that's why I'm asking if that would be too much gear for a 408? I've been told they don't rev as much as my current 340.
Depends on how much HP the 408 makes, and where it makes it.
i.e. when I made somewhere between 467-500hp range at high 5k RPM range or so RPM. 4.56 gears were perfect. I'd run it out the back door of the 1/4 around 6000-6200RPM in 3rd. In the 1/8th mile i'd run 6200 through the traps in 2nd gear + OD.
When I went to my new engine, Which makes 602hp @ 5900, I couldn't get through the traps unless I shifted into OD and it would fall on it's face and be low 5's through the traps. I switched to 4.10 gears and now trap properly in 3rd gear.