I don't think a chunk came out of that piston. I think it got hot and started to flow, it looks more melted than impacted. Doesn't this truck have really low miles? I think I'd try getting a new standard or maybe try to find a standard + piston and see if the wall will hone out. I don't think you have to go for perfection here. Did you run a compression test on it before you pulled it? If so, how low was this one? If not that far out, a new piston and bore polish might bring it right back into the game. As Wes has demonstrated with his various projects, these engines can run pretty well with all kinds of maladies and if you can minimize the problem here you might be smiles and dollars ahead.
Also, try the WD40 Rust Soak on the lifters. I've had great luck with that stuff.