Looks like they are identical. On the MB website 16 yr overview, they have them both lumped together:

http://www.mbusa.com/brand/container.jsp?/overview/overview_engine.jsp?spec=3&subNav=overview&yearModelCode=97_S500C&class=97_S&rnav=012345678&menu=3_3

They only brought in 2387 of the '96 and 933 of the 97's.

Gilly