5/6pk belts/pulleys is what i was looking to run when i was planning to g60 mine. I would say that toothed would be ok but wouldnt wanna hit that rev limit often on a g60. Most people i have spoken to with g60's run the 6pk belts.
It could be a load of lies but im sure i read that the difference in top end boost pressure (when the v's would slip) between multi v and toothed was like 0.1 bar difference. Not sure what difference it would be on a g60 charger though
djtez is currently doing a g60 conversion and is using 5pk belts/pulleys.