ARP VQ35 Head Stud Kit for the 2003-2006 Nissan 350z is good for people staying under the 500Rwhp range. Anything over 500 Rwhp we recommend upgrading to the L19 studs.
ARP recommends the use of head studs over bolts whenever possible for several key reasons. First is the ability to obtain more accurate torque readings because studs don’t “twist” into the block. All clamping forces are on one axis. By the same token, there is less force exerted on the block threads, which contributes to improved block life (very critical on aluminum blocks). Finally, there are factors of easier engine assembly and proper alignment of the heads every time.