Being a fireman on the Huckleberry, and having fired 464 quite a bit this year, I will attest that she steams great! During the overhaul of 464, amoung the many things our crew worked on was the smokebox. We replaced the lower portion of the entire smokebox, including the ring at the front. It also received a doubler plate (I am unsure if it had one before, but I think it did) and a new fabricated blast pipe, along with some miscellaneous plates.
Marty, John, or Clive, would you please elaborate?