pinning crankshaft

The guys that run superchargers do this all the time to keep the blower crank pulley from stripping under high boost. I’d get a new balancer since you’re going to the trouble, but I wouldn’t worry about it being strong enough.
i'm far beyond the torque needed to turn a blower. Unless one more 1/4" pin will hold back all the torque this little 318LA has to offer.