I think small blocks had a bolt on middle crossmember and big blocks were welded?. You would have to look at it close up I'm afraid!,you just cant tell enough from the pictures. For that price its probably a high milage driver (like what 77CVT says!).Plus its weird that it has round exh. outs, they should be square like you said....smells of a prior accident. If Joe is selling it for 42750 he probably bought it for $15000 US, so it probably needs a bit of work! BUT its still a reasonable price for a Big Block if its in reasonable condition!