Just remember that bigger is not always better when it comes to cams, especially on small-displacement engines like the 4.6 (281 cubic inches) that are hurting for torque already.
Big cams move the powerband up in the RPM band. If you don't do valve springs and don't do anything to strengthen the bottom end, you'll still be limited to a safe value of ~6000RPM and thus the power gain potential available from big cams is basically lost. And while the power band is moving up, torque is often lost down low, again, not a good thing on a small-inch motor already disadvantaged in this area.
For a stock motor on stock springs a "Stg 1" cam is a good bet. I've got Comp 262AHs on mine and when normally aspirated the car picked up ~25HP near redline without losing anything down low. There's a slight idle with them too, if that matters to you.
If you're in it for a lumpy idle I can't help much except suggest that, since you're going to need an aggressive cam, you upgrade the springs too.