It's an aftermarket aluminum pulley. You might want to remove it and inspect the inside of the fit area. If it was wobbling. It might have egg-shaped the inside. When you retorqued it. It may be just sitting on the flat end of the crank, and not on the circumference fit area.
And yes, an aftermarket aluminum pulley WILL break the crank shaft. I found out the hard way with an LT1 350 I had in my one truck.
just google it.
https://www.google.com/search?q=brok...ih=591&dpr=2.5