The "656" casting could be either a passenger block or a truck block, but given those 333 heads, let's assume it's a truck block. Nothing wrong with that, but a good passenger block is harder to locate than a good truck block.. That "881" aluminum dual quad intake was cast to fit the high performance heads, but can be trimmed to fit those low perf 333 truck heads. A scope might tell one more about the tops of the pistons, but it always best to get the details on record with an invoice, etc. Popping the valve covers tells you a few things as well, but far short of the whole story.
Not knowing those details gives you an advantage in negotiating price, if it comes to that.
Good luck in your pursuit!