Also even some 350 heads (882s for instance) are vulnerble to cracking and warping. The real advantage of certain heads like 993s is their rigidity and resistance to cracking. Some of that is lost when you install 2.02 valves and or port them extensively, but at least there is enough material to remove and not compromise your main goal, which should be reliability, unless you need an excuse to bring your girlfriend home late, and you like changing cracked heads.=] I have never magnafluxed a set of heads, but I wouldn't even consider it w/ any 305 head, because you can depend on them to fail if you run them hard...