There are many brands of slant six gaskets (or at least there used to be). When I did my first turbo slant, I was having problems with detonation (unbeknownst to me) and blowing gaskets. So I opted to go with "O" rings and copper gaskets. Big mistake. The gaskets blowing were like a fuse blowing. It was protecting other parts. After the "O" rings I started breaking rings, hurting pistons, etc (FROM DETONATION). But I didn't blow any more gaskets. I know several turbo slants that are not running copper gaskets, and not having problems. I still have my "O" ringed and copper gasketed engine, but not having those problems since I finally realized my problem. Copper gaskets on a street type car CAN be a pain in the butt.
PS: The main reason for my early problems. Could not hear the detonation due to the exhaust and turbo noise, Lack of the availability of a "boost timing master", and/or a wide band O2 sensor. All I had was a EGT from an airplane.
PPS: I was running around 10-12 lbs boost.