B is for Brumfield
F is Finley
Larry Brumfield and his partner made heads patterned after the ("head with the LARGE B" aka Police head from 1931) starting in 1980s.
First heads were about 5.2 to one. 5.9 came later. then the Super Bs of higher compression.
http://www.fordbarn.com/forum/showthread.php?t=8663
for more details: