Which wire for an O-ring

Our slant six/turbo blew a head gasket last week, showing 50# compression on #1 cylinder and 60# on number 2/ Those numbers have always been 160/160 in the past.


We are going to take the hint and install O-rings around the cylinders, but have heard varying opinions about which wire to use; copper or stainless steel.

Any opinions?

Prine???

Any information will be appreciated.