I have a C6ME-A 390 Block dated 7C27. It came out of a 1967 Mustang.
I purchased it as a spare 20 years ago. It had been stored inside when I bought it and it's been stored inside since. When I bought it, the bores had been coated with grease. I added more grease to them and it's sat that way since.
Never been bored... standard 4.05" bore. I am not aware of, nor see any damage of any kind. The engine was assembled and turned over freely just prior to purchasing it.
Pics to follow
I truly have no idea what a standard bore 390 block is worth. I looked around ebay, craigslist and the FE forums and decided that $800 seems like a reasonable number.
If I assume a 1200 mile shipping distance, Freight should be approx $175 including tax using Fastenal.