Welcome to the club! :cheesy: I've stripped both of the ones I tried to get out with the engine in the car. In both cases, there was enough of the teeth left after the initial stripping that I put a Torx bit on a breaker bar, and used the weight of the engine to keep the bit and breaker bar clamped between the car's body and the bolt so it wouldn't slip, and got it loosened. That worked both times. If the engine's out, I'd drill the head out, pull the sprocket and the shaft it sits on, and there should be enough of the threaded shaft left to grab with some vice grips and unscrew.