For a real ZZ4, the block casting number is 10105123

For a real ZZ4, the head casting number is 12556463, they are aluminum

You have neither so you dont have a ZZ4 engine.

your block casting number is a 1995-1999 350 for either a boat or a truck and has a 1 piece rear main

the head castings are 1987 to 1996 passenger car heads....not vortec (vortec heads have only 8 hold down bolts)

sorry

mike in tucson