There goes that high-octane Premium fuel thing...

Some people will argue that its ok to run Reg on these performance cars.

Sorry to hear OP. I would opt for replacing the engine if possible with a stock one and use your salvageable mods on it. We don't know the full extent of the internal damage so it could be worse. We also don't know the history of your vehicle so that is something you'd have to elaborate (mods, maintenance, fuel, etc).