Cracked 350 Crank, build 383?

[57taskforce]

Makes me kinda wonder if the thrust bearing isn’t out of it. I guess it’s possible to be cracked and flexing but I would expect it would only flex once or twice before it broke all the way thru and the balancer wouldnt be turning if it even ran at all. Thrust bearings seem a lot more likely in my mind. They can and will make all kinds of noise with the crank walking back and forth. I guess that internet diagnoses also depends on the direction of the play, if it’s in and out thrust bearing is my bet, up and down... not as likely to be the thrust...