Unfortunately, you likely won't find a set of cylinder heads without cracks in them, unless they are brand new. Some cracks are considered acceptable and some aren't.
I went thru 3 sets on my engine build before realizing I wasn't going to find any heads that were crack free. Ended up having my machine shop guy put pins/lock n stitch in the cracks on both heads. Was very happy with how they turned out and didn't cost an arm & a leg.
It can be easily done if you find the right guy to do it.
Might be an option if you can't find a good set.