I am buying a 2004 ls6 out of a GTO. I am converting it over to a carb. and was wondering if anyone knew what cam to use with 243 heads. Or how to make it to 400+ hp.

 

My crate LS2 with 243 heads, single plane intake and stock LS2 cam (basically a slightly fatter LS6 cam) was rated at 440 HP from GM.

So just bolting on a carb intake with a 750 cfm carb and you are above your HP goal.

As for cam lots of options. You need to decide what you want to do with the car and what supporting mods/gearing you are going to do before you can decide how much cam you want to live with. There is no one answer.

The LS6 cam you have is no slouch.

 

The 5.7 from the GTO was a LS1.