[REAL 1]

A good 427SO block that passes magna flux and sonic and is not a "service" block will run you $4000 to $5000 easy.

If you use good original heads, original manifold (if you can find this stuff) as opposed to replacement Eldebrock heads or manifold or Blue Thunder manifold things will get even more pricey.

A good original iron block 427SO with "original" stuff and quality parts (ie Harlan Sharp valve train, roller rockers etc, etc..)will run every bit of $20K to $25K. An aluminum block will be in the same range maybe slightly more if you go with Shleby heads and valve train. Expensive but quality stuff.