The gearbox and driveshafts can handle up to and probably beyond 300 bhp thanks to German over-engineering and anyway it's torque which breaks gearboxes. I'm sure the engine can handle the relatively modest levels of torque a charger produces. The power of the supercharger is progressive which helps limit the strain put on these components and means that traction isn't a huge issue. You'd be amazed what difference good tyres make. The current supercharger kits are designed to run on a standard engine. No need to change the headgasket, pistons etc. You'd only consider that if you blew the engin