RS485 Driver (75176b vs. sn75176a)

Hi,

I've got a board which is supposed to be RS485 compatible, but it contains a SN75176a (RS422 part, according to the spec sheet http://www.ti.com/lit/ds/symlink/sn75176a.pdf).  I can't seem to find any electrical differences between the "A" and "B" (RS422/485 according to the spec sheet http://www.ti.com/lit/ds/symlink/sn75176b.pdf) versions of the drivers.  Am I missing something critical between these two drivers?  Is there any reason why the "A" version couldn't be used in a 485 application?

Thanks!