[undy]

Your duration looks like it's right in the ballpark where it should be. A little more lift might help, around the 0.600" range for an semi-agressive street/strip mechanical flat tappet. If your cam's been around a few years I think you'll find the newer grinds to your liking too. Lift and valve load are the determining factors for your springs. Cam tech for whom ever can advise accordingly. Keith could probably recommend a specific manufacturer and grind targeting your existing combo and what your looking for.