Most up to date motor shops dont O ring blocks anymore, there is a gasket that they use now that most good shops will know about that makes O ringing a thing of the past. Even the Turbo cars in the fastest street car style shootouts that are running super high boost are using these gaskets without problems.
The shop that is building my blown 540 is using the gaskets as well on my motor.

I know the name of the gasket but have no idea how its spelledso i'm not even gonna butcher it by tryin to spell it

BG