maximum bore on a 5.3 block

[Sleaper]

You can bore it to stock LS1 bore. I believe that is the max. like 3.903 or 3.905. Something like that. I dont believe a 4" would fly on a 5.3
However that just happens to be stock 6.0 bore though.

That's correct. You would bore the stock 5.3 from 3.78 to 3.90X or about .120-.125. That's the max you can go without running into cooling issues.