1978 ABS first introduced on W116.

He says they were an expensive add on since 1978 and became standard in 1985.
I just saw this on youtube:
Introduction to Mercedes Early ABS Systems by Kent Bergsma - YouTube

My wet dream car would be a 1985 300TD with ABS (someday convert to 5 speed) perfect 10 would be to use the cosgrove 5 speed out the M3 Killer and an upgraded turbo)