With a 454 I'd be tempted to go 3.73 but I dont have any real world experience with that combo. 4.56 is really low and pretty popular with the 4x4 crowd you might be able to trade gear sets for nearly free.
Using the gearing calculator at
http://www.grimmjeeper.com/gears.html it looks like 3.73's would drop almost 600 rpm's at 70mph compared to 4.56's.