I've got a copper head gasket on my 3T-GTE. I've had the block O ringed and a reciver grove in the head and the last time we put it back together (engine builder and I) about 3 years ago we use a salastic type material call 3 bond. The engine builder & I used it for every thing, head gasket, water pump, timing chain cover, etc...
With the copper gasket I had to tourqe the head bolts to 75 pound. Having said all that though, after the Toyota National drag day I found some oil in the water which I don't know where it came from yet.