The Camaro must have been REALLY ignored for it to be THAT bad. I suppose if one had been neglected that bad, I wouldn't vote for the motor flush either. 100 mile hot oil changes for a while would be the key if it were that bad.
I have used the flush a few times, but it was in an engine that was just a little dirty, not completely caked like the engines with Amalie or Havoline in the sixties used to get.
Have a great day,