Mike, What is the truck your putting this engine in? What are your plans for it? I would carefully concider before removing the Vortec heads. They are the best flowing stock GM heads & likely better than many ported heads, ported heads for a race engine (big intake ports, ect.) with good high lift numbers are not necessarily what is best for a truck engine.You would be taking improvements that GM has made (roller cam & good all-around cylinder heads) & throwing them out. The valve size isn't the whole story. What cc's are the chambers? If they are 76cc + a deep valve job, your going to lose about a point in compression. Myself, I would purchase a hyd. roller cam (the GM pt# 24502586 is a good one for general performance) & some beehive springs & put it in & go. This will make you a good all-around engine. Lorne