Wow. Never seen a member do that. Is it a four speed?
Do you have a trans brake?
I think you may have had some really porous contaminated metal there from the factory. Chrysler was not known for pretty precision welds anyway.
My steel member has never done any cracking in all the years that I have abused it. Maybe the drive train was out of alignment? Strange.

As far as this alloy member, trust me when I say that I have given it all a good thought and studied every possible way that it could/would fail, so that is why I have come up with the extra material pill box, 6061-T6 material through out, stress relieved radius corners and a constant visual multi-point inspection of the car and its special parts before and after racing activity for peace of mind.

I appreciate your concern.

Could you believe that back in the day in the name of saving weight, Factory engineers, Pontiac engineers as a matter of fact came up with the cocky idea of creating an aluminum exhaust header for their Cheese cars. Who would think of such a crazy idea knowing that it is no less than a raging furnace at those points. Of course they failed and pretty much melted like the wicked Witch of the West in Oz.
As far as the cheese frames, well those did not fare well either in some cases.