i am going to go out on a limb here and guess the sportsman 2's. below is an exact quote from thier site about the heads. unless the vortecs have had a litte work done to them you probably wont get a 30 to 70 hp gain as with the sportsmans.


Continuously improved since its 1987 introduction, the Sportsman II is still the industry's most popular cast iron high performance head. Featuring RightCast® 200cc intake runners, Fast-Burn chambers and your choice of angled or straight plugs, they're good for 30-70 horsepower increases right out of the box. They are the aftermarket's only 50-state emissions legal cast iron high performance cylinder head (E.O. #D-343-1). You should also know that all World Products heads are precision CNC-machined, and indexed off the chambers to assure perfect alignment with the cylinders.