A person would have to call them to see if they can do a B engine since most advertise T & A engines. There may be others that don't advertise on MAFCA or other sites. I don't have any idea about their work or whether they are still active.
Pirranio's Antique Automotive in Denton, TX Geared towards performance engines.
Mr Model T (Ross Lilliker) in College Station, TX
Snyder's Antique Engine & Machine in Albany, TX