Oversized Gasket / Copper Gasket Etc?

[Richie-Van-GTi 71 2 Cars]

As per previousd threads Im using 2 head gaskets at the moment but I intend this to only be a temp measure for setting up purposes. Both gaskets are given as 1.4mm by the suppliers, not sure if this is before or after compression? I want to start looking for replacements and need to know, can I buiy an off the shelf gasket that is around 1.6-2.8mm thich or should I be looking at a copper gasket? Are copper gaskets suitable for cast blocks and does anything else need to be considered into the equations?