ARP's all the way!!. I heard an anology that made a lot of sence, it went as follows "Imagine your in a school and someone's pulling on the door classroom door but your trying to hold it shut, if he's more powerful he'll get that door open no problem. But, picture this, your a dude holding onto one classroom door and the other across the hall, it'd be impossible to open those doors no matter how much he pulls!". Pretty much what that means is that since you have one part of the stud threaded into the block and the other through the cylinder head, then a nut. Once you tighten the nut it will be super secure. Plus, your old re-used head bolts will be stretched and will cause the head to lift!!!.