No machining required for the LS6 yellow springs. I just pressurized the cylinders on my 5.3 and changed them like that. I wouldn't trust any stock LS1 pushrods with this cam because I heard they have a tendency to bend at higher RPM/spring rates. Some chrome moly stock length rods will do fine. Make sure to get your ECU reflashed for the cam and for the tranny to shift at higher a RPM