I Just replaced the "Smog" heads on my 1976 Monte Carlo with a 350 CI small block, 4 days ago. I had a hard time deciding between the Vortec heads and other Aftermarket Cast Iron heads.
Because I already had a Edelbrock "Performer" manifold I went with World Produsts "Sportsman II" heads. WOW what a difference, the engine is making a lot more torque and HP and really moves the 3900# Monte down the road. The heads were $850 for the pair and were ready to bolt in place.
If you are on a limited budget, the Vortec heads flow very well according to the research I did and are a couple hundred dollars cheaper than the World Products heads. Hope this helps.