It's real important for ARP, probably less so for you. A Volvo B20 is probably one of the most over-engineered engines ever. I rebuilt a lot of B18 and B20 engines and I never used a new set of studs and never had a head gasket problem. With aluminum heads, it is a different story as the aluminum expands and contracts a lot more than cast iron. Some systems are designed to stretch the stud to use elastic and tensile properties to keep the head tight through warm up and cool down cycles. It is not unusual for these to be one-time use studs. Just make sure the threads are clean so you get an accurate and consistent torque.