ARP recommends the use of main 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. Finally, the there are factors of easier engine assembly and proper alignment of caps every time.
There are many important reasons to use ARP main stud kits including the elimination of main cap walk and fretting, as well as protecting the threads in your engine block. All kits come complete with hardened parallel-ground washers and high quality nuts. The studs are manufactured from 8740 chrome-moly steel, heat-treated in-house to 200,000 PSI tensile strength, and precision J-form threads rolled after heat-treat to create a fastener that has threads 2000% stronger than others.
For 2004 & later models with factory girdle (block stiffener plate). 0.600 counter bore.