If you get the O ring and receiver groove depth and width proper it, the O ring, shouldn't hold the head away from the block enough to worry about sealing the oil and water passages, unless your going to use solid copper head gaskets
![twocents twocents](/ubbthreads/images/graemlins/custom/twocents.gif)
If you choose copper head gaskets then use a thin layer of silicone as you like
BTW SCE gasket makes several different types of copper head gaskets, one has a built in O ring in them so you only need to worry about machining the receiver groove in either the heads or block
![work work](/ubbthreads/images/graemlins/custom/work.gif)