The recess for the factory bolt isn't large enough for the ARP bolt...it needs to be opened up to fit flush, if you will. Reason why I just went with L32 rods and factory GM TTY bolts...didn't want to **** with it.
THAT, is your call. I think Head Studs at a minimum, but Main Studs are nice as well...I never have to buy head/main bolts again...and I'm not sure there, I have a local hookup so I get a good deal on factory stuff. Not sure if your auto parts stores sell them...