While at the local car show, a guy told me he has a garage full of Y-Block parts he wants to sell.  Among the parts are a couple of complete engines.  He says one of them is a 312 with a 2V intake manifold that came out of a Mercury.  The valve covers are stamped Mercury.  The automatic transmission is still bolted to the engine.  Did they ever make any 312s with a 2 barrel carb?  How can I tell if it's a 312 without disassembling it?  Is it worth anything substantial?