If you don't want to sacrifice driveability then stroker is the way to go.

4.25 crank goes in with little to no clearancing for 508 cubes. The new Trick Flows seem to deliver the most bang for the buck out of the box.

Driveability is all about the camshaft and Dwayne Porter should be able to spec you out a cam that will more than meet your requirements while still using stock rocker gear and having idle quality approaching your grandmother's New Yorker (after she swapped in the 6pak cam, Granny was from Pasadena ya know!).

Kevin