I purchased a used built long block to stick in my track car.

Due to signs that there were issues with the HG and a few other things I decided to pull the head and refresh a couple other gaskets. That is where I discovered some additional issues that I simply want an opinion on.

1. It appears some water/coolant or cleaner found its way into the combustion chamber resulting in a calcium like build up of rust where the rings were sitting. This ridge of rust was completely dry and not something that could easily be rubbed off. Thoughts on how to clean it up without pulling the crank?

2. It has aftermarket cams w/HD springs and one of them shows signs of scoring on a couple lobes of the cams. This scoring or surface imperfection can be felt with my finger. Is this cam shot and will it continue to deteriorate?

3. The block also shows signs of wear from piston slap. You can clearly see where the scrub marks in the cross hatching. How can I tell if the bottom end is a good build? My concern is that was a simple drop in build with pretty much no effort put into bottom end preparation. Basically how can I be sure the short block is healthy as I don't want to sink time and money into this motor if it could be a big pile of slop.

I know there are unknowns buying a used motor but honestly there are unknowns when buying a new rebuild from a perf shop as well. We've all seen the horror stories from both approaches. As long as I can validate the health of the bottom end I could live with the issues. What is the best way to do this?