I know full well that .020 pistons are still available. I also know that every now and then a person might want to bore one to that. However, most people don't. It used to be much more common to bore one .020. I have even seen engines rebuilt by Jasper that had only one hole bored .040. That also used to be standard practice, but not any more.
This post is the first time I have heard af any one boring one to .020 for years.
As far as saving the bore to bore it out later, how many times would an engine need boring anyway?
Momo, you need to find out more information about the engine, other than it is shiny. So far you haven't given anyone any information as to how to determine what kind of HP it could have.
Valve covers, water pump and fan blades don't make engines fast.
Ed