I'm not sure why they used round keyways, maybe because the section at the shear line is maxxed out without weakening the hub much. The way that they fail is that folks pull the harmonic balancer and bugger up the pin holes when they reinstall.

I am skeptical of drilling new holes successfully because getting a precise hole seems very very difficult to me.

When I had the wobbling hb my favorite machinist advised me to get another crank. If he couldn't drill a proper new keyway I don't see how a hobbiest can do it in their garage with hand tools.

It doesn't hurt to try though.

The alternative is to tear down the entire motor and put in a new or good used crank. Just the labor to tear it down and reassemble is probably 2K.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.