My opinion is if it is a VVT engine do the 58 tooth if it is not I would do 32. It will be more desirable to a VVT guy with the 58 tooth. I have spoken to MSD just about everyday for the past month bugging them to update the 6013 box, which they say is in process. Once that is done it's an easier decision. I have a 58 tooth 6.4 right now sitting because the fast box is junk and won't control the timing and the MSD will not work yet. So a carbed gen 3 with a 58 tooth wheel is screwed other then using a MS gold box just for ignition which is a really expensive option.