Whats needed to fit roller cam into my 1971 340?

cam and lifters should drop in. The hardened distributor drive gear is not needed. The machining sometimes will address the shallow lifter bores of the 340 that would otherwise uncover the oil band of a traditional roller lifter, but in this case they are only referencing the optional smaller locking valve seals and Comp valvetrain. Rollers offer more aggressive ramp rates so you ll need recommended valve springs. $$ Rollers are great for max effort motors, hydraulics still have their place too.