We recommend a NGK TR55 for most pump gas naturally aspirated motors and a NGK TR6 for most mildly boosted/nitrous applications.
No, our heads can only be flat milled due to the fact that the intake cannot be corrected
3) Factory Components:
Yes, all factory components will be accepted except for perimeter valve covers on the 97-98 year LS motors. Center bolt covers will be needed for those 2 years.
4) Torque Specs:
Head bolts should be torqued per the bolt manufacturer’s specs. ARP typically recommends 70 ft.lbs. on the 11mm bolts and 25ft.lbs. on the 8mm bolt. Head bolts should always be re torqued after the motor has been heat cycled once (Brought up to operating temp and allowed to cool back to ambient temp).
Visit the following sites for information regarding choosing the correct push rod length.