I agree with how to clean this block, but to me, that seems like a heluva lot of time and expense for an iffy block unless you already have the tools and equipment. Why not take a look at the GM Performance Catalog - a new block or even a full crate motor might be a better way - especially if you have some constraints. Here's the block section:

https://store.gmperformanceparts.com...ategory=Blocks


....and the crate motor section:
https://store.gmperformanceparts.com...Small%20Blocks

I've seen Apple Chevrolet advertise them at less then what this catalog says