A friend of mine works at a late model yard. He says he's seen alot of cracked vortec heads. By the time they get them, he figures they've seen too much heat.
Better off getting new castings. By the time you purchase the heads and send them to the machine shop to get pressure tested and then rebuilt/modified - you could have about paid for new ones!!
Check out
www.paceparts.com
or
www.goautocenter.com
or
www.sdpc.2000.com
Should be able to get them for $220 each - complete or $290 each modified for hyd.roller cam w//525 lift and screw in studs.
Stock vortec heads won't take over about .450 lift. They flow great, but don't over heat them! Make sure your cooling system is top notch.
Scott