Most people will tell you that x-drilled rotors are a waste and that blanks are the way to go. X-drilled rotors do help the pads vent the gas/heat made under extreme braking, but at the same time there's less surface area for the pad to make contact with. They're also more prone to cracking/warping. Slotted rotors also have less surface area than blanks (and also have the bad habit of eating your bads for breakfast).

Both of the above are primarily beneficial in situations where excessive heat will be produced under braking. However, for street use (and especially with today's brake pad technology), heat dissipation is becoming less and less of an issue.

As to your second question, I don't know an answer right off the bat, but I'm almost certain you have to replace your entire front or rear brake assembly with the system from the LS/GSR.

Bottom line: Blanks are fine for almost all applications. I personally think slotted rotors are underrated and I'm going to try them for myself the next time around.

Shingo