Hey colin,
Wonder if any read what you wrote ?
Or if any , who bid, looked at the pics

I see the same thing that you see,eh...namely the BIG chunk out the side of the B block, that is welded. That could explain why for sale ? When spending over 4K , so far, for unknown head, do you think that someone would ask the guy to take pan off and show bottom end ? Easy to do, but people seem to have LOTS of $.
FWIW....I asked the seller to remove pan and look/see with pics for bidders sake. Ten minute job....Refused !!