When you do the ARP rod studs, the rods have to be bored back to factory spec I've been told, as they deform the large end. I had this done when I recently built my motor but I have also heard it is not entirely needed.
There is a problem with the ARP Mains. They don't have an accommodation for the oil pick up. They are studs so unlike the factory bolts which have the smaller "Bolt" for the pick up to mount to, the ARP mains dont.
You don't even have to remove the head to replace the headstuds with ARP's so why not.
Head studs are a no brainer as said before.
Rods, I was building for 350+ so I figured it a good idea.
Mains, if they aren't deformed, probably not totally needed for anything less than 350-400. I did it as precaution.
/brox