I say 427 topoiler. The reason being the 427 topoiler had the
oil pressure relief valve right above the cam plug at 12:00 like that one shows. That block has the wrong plug there and should be checked inside for the relief valve and spring. If not they can be bought from vendors like Doug G. Std 428 or CJ did not have that feature. Next brass freeze plugs or what looks to be anyway. Marine or industrial. Last the boss for the sideoiler relief valve is not machined nor is the plug that would be on the face of the block either. Rick L has very good advice on inspection. Just my take on the block ID.