I bought a NOS service block in 1993. The company I purchased it from built the entire engine. I installed it in my car in 1994. I've thrashed it pretty hard over the years and its still performing well!!
Four years ago #2 cylinder wall split.
The cylinder wouldn't have split if the intake valve springs hadn't broken and let the valve drop against the piston at 6000+ rpms.
The aluminum head took a beating also!
After that failure, #2 cylinder was sleeved and other damaged items were replaced. Today it still runs great and makes a lot of power.
I have no opinion on the value of the block you're asking about. Other folks will chime in with some good information.
David