I've heard it's only a few cfm, but I'm not sure. I wouldn't think it would be more than 5rwhp or so. Anybody know for sure?

 

What supporting mods would I need for this cam? basically, would I have to modify anything in the heads, or could I leave them stock?

 

Do some research. For a cam, essesntially, you need:
Converter if automatic
Headers/exhaust
Most to all bolt-ons to get the full potential, as well as a dyno tune. The bigger the cam, the more a tune is REQUIRED for it to run properly at all versus just to get the most out of it.
Springs (duals are safer, usually used for higher lift cams)
-some springs require new retainers, most spring kits come with lighter Ti ones
-some require new spring seasts, again, the kits come with them
Nothing needs to be done to the heads or pistons with this particular cam