I have been studying my Basic & Expert D&D sets (the Moldvay/Cook sets), and I still argue that they are the epitome of D&D. The best in my humble opinion. While reading the example of play for the who knows how many times, I decided to map it out. I am sure I am not the first to do so, but I wanted to see what the Moldvay Haunted Keep dungeon looked like (even if only a small sample).
So, here is what I found. I love the 20' wide corridor, never see enough of that. I had to guess at the final secret door in the south (where the hobgoblins attack on pg. B28).