J spaulding

Did Mercedes ever put a "V8" insignia on the right side of the trunk on a 1999 or 2000 SL500?

SRHsl600

not in my observation, the V12 yes, but other engine sizes were the 300,320,500, and 600. I have not seen any western pacific vehicles however.

MB-Dude

Not sure; never seen it on any model. That said, your local dealer's parts guys should be able to call up the parts list for the trunk lid. On that drawing will be all the known USA emblem/badging options for MB production models. I suppose it's possible an after-production styling company (i.e.: Brabus, Lorinser, etc.) may have put something on the trunk lid, but do not know for certain.
Cheers,
Jeff