You need to resign yourself to the fact that almost nobody machines cylinders or cylinder heads properly. So that when a rebuild, even if just the top end, is being done, right away there is a significant challenge in getting those parts to spec. This is a fact. I have written elsewhere on this, so I will point you toward those articles. On the cylinder head side especially, there are many layers of understanding that have to be navigated. Check out the articles.

Cylinders done right
Valve jobs done right