some pics of my engine before Assembly

[flav]

Well the answer is quite simple really.... :D
The copper will crush down and fill the O ring groove in the block as the steel one wont. However, i have used the steel ones with the std gasket as long as the fire ring is cut out. This worked very well but im reluctant to go to deep into our R & D areas as it's taken years of work to get this far....but ZOOM Secrets do get out!

OK....If using the Old style gasket you will need to measure the 'crushed' thickness of it and check the current O ring protrusion from the deck, it has to be, obviously more than the gasket! This can also vary depending on things like head bolts and gasket cements (arp bolts have a much better hold). I find that .3mm above the gasket with the fire rings removed and a very light brush on both surfaces with 24hr araldite will hold it extremely well. Try this combo and you cant go wrong..probs is, when the O ring doesnt protrude then you have to get thicker wire than the groove and roll it until you get the correct amount. Hopefully the machinist compensated for this when he did the block.
We used this method on all the long distance race engines we built for GRP A..... Not 1 failure.

[RiceThief]

Thanks flav, this will give me something to aim for then.