As started above, it relates to one- or two-port cyclinders.
Any of the Cox .049's can be switched back & forth, creating the following options:
Babe Bee or Super Bee
Golden Bee or Black Widow,
Medallian or Tee Dee.
The two-port cylinders clearly produce a lot more power, but nothing is free, they run out gas a lot sooner, too.
The Super Bee was assembled to get the P-40 Warhawk off the ground, it wouldn't do that with the original Babe Bee.
ps: The high compression "trumpet head" also gives a nice boost, compared to the low compression "hemi".