The letter B only means that you are using either mask 0L85D or 1L85D. These masks contain tons of silicon bugs, here are the two major ones:
- The SCI interrupt flags aren't working correctly. If you want to use SCI and interrupts, you don't want to use this mask.
- You can't secure the flash/eeprom if your program is writing to them in runtime, because they will be secured from internal writes as well.
It is all in the errata. Note that most Freescale retailers are clueless about the above, so make sure to specify that you don't want any 'B' in your order. Freescale stopped production of the 'B' masks this winter, but there might still be some out there. (Though the market was pretty much emptied of HCS12 ICs last year, because of the long delivery times).