Stefano,
If that is what the Serial#/ID code at the bottom refers to, then that may be what it started out as (It is a 512 block). But as you can see at the top of the receipt that he paid for and received a 427/450 ZLX equipped engine. He stated he picked the engine up and ran it in his 55 chevy until it dropped a valve in the aluminum heads. He then pulled the engine, sold the 55, bought a 70 Z28, tried to get the heads fixed and was told it would be too much work, he bought a set of 990s and then started getting the Z ready to race. Never quite finished car and I purchased the Z28. I then installed the engine in my 73 Z28 and ran some low 11 sec ets until I hurt a valve. I then had the engine rebuilt and it is still in my 73 Z.
In this car running 8.70s now!!
Paul
630-878-8870