ShadowDrake

Well the pistons are only slightly stronger than the rods. The crank can take a bit more than either of them. The rods are RATED to 450 HP, that's flywheel, people are running around 400-410 RWHP (which is closer to 500 at the flywheel) without problems. I'm not sure what the rating is for the pistons, 480, maybe more... but they're hypereutectic... so they're brittle and will go when you get detonation/pinging with any type of forced induction (which you'll need to get to those power levels on the 4.6). If you're swapping the rods, do the pistons at the same time... you should do the crank if you can afford it and just have a totally forged bottom end that you won't have to worry about till well over 600 HP.

VTX1800N1

The cam chains are not affected by the horsepower of the engine. The only factors that affect them are valve lift and RPM.