318/340 cranks ???

I have a 318/3 318 steel crank in my 340.

Seems that a PO had put an aftermarket converter on it and failed to put the balance weights on it. Shook it so bad it broke the crank in the #1 main bearing. Sorta like taking a bottle of beer in your hand and shaking it as fast as you can with your elbow strapped to a table.