I've done 120 with room to spare (though not a lot).. maybe 125 if you're really trying, and a little more on a downhill. Can't do so well now since I got wider wheels + rubber (more drag + more friction!) from the 16v.
By the way this is a worthwhile upgrade - the classic 15 hole MB alloys look good, especially as I had mine repainted + lacquered, and the ride *improved* noticeably (less unsprung weight, bigger footprint, not too low profile tyres 205/55 R15), and there's huge amounts of grip on any turn, at any speed (but can still unsettle rear in the wet!)
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black