A lot of the noise really comes from the injectors into the intake and why the 2008 LS3 for C6 was redesigned so that it now has a top hat that has foam in it to muffle the sound.

Its hard to say without hearing the noise but alumimum blocks allow more noise to be heard then when steel was used.

Depends on the CAM grind, the LSA and what type of overlap on how the sound is but as long as your sure the correct length push rods and rockers used then assume most noise is natural to the CAM design