If that would have been a hypereutectic piston you would be shopping for a block right now. That kind of damage is normally caused by severe detonation or possibly a cylinder full of water (hard to tell by one photo but I'd wager on the former). It was not the piston's fault - that I can promise.
Get another set of forged pistons. The Edelbrock cam kit is nothing special - - I sell the same basic grind for less dough. But that's not important part - you need to be certain to get decent quality AMERICAN MADE lifters. Many of the big name guys are bringing in cheap stuff from Mexico or China. That junk'll kill ya. Ask and check. Then use GM EOS with Rotella or Delo
oil for break in.