I have had experiences with o-rings. I will start off by saying do NOT use o-ringed heads. That type of thing is for someone running some ungodly amount of boost or nitrous. And even then, a lot of guys don't use them. They are nothing except a pain in the ***, and you'd better hope the ring grooves are cut deep enough. Mine weren't and I couldn't get them to seal. They are more trouble than they are worth, not to mention the gaskets cost more. There are 2 good reasons not to use them, one is what someone else said. Think of the head gaskets as fuses, I'd rather blow a gasket than break a piston or rod. The second is that if you need o ringed heads with 15 lbs of boost because you have sealing issues, then there is something else wrong. 15 lbs is not worthy of o-rings. I can only suggest from my experience not to use them unless you have a race car. I can also attest that I am not the only one to have problems with them. Also if you ever have to remove the heads because of a problem and find they are warped and have to resurface them, then you have to regroove them. I also should note that with o-rings, the head must be exactly straight. Most of the time the head can be out a couple of thousandths, but if it is with those damned o-ring gaskets, you'll have sealing issues. Take what I've written for what it's worth.
Also, if those heads on eBay have ever been installed on an engine, even if for 2 minutes, then walk away from them. You can get brand new ones for that. And if you should decide to buy them, you'll have to drill the bolt holes out to 1/2". Easily done on a drill press.
