I don't know but I asked Todd Knutspn who does and he said:
The 1980 US 450SL has a rear axle ratio of 2.65:1, which is unique to
the 107 series SL line. It is a one year only ratio, changing from the
earlier 3.07:1, and in 1979 3.06:1 ratio. The 380 and 560SL's have
2:47:1 ratios, so that is also not an exact fit. I'm pretty sure that
116 chassis speedo's interchange, but I could not find any ratios that
are any closer as the rear end ratios in the US changed at the same
time, and they too had the 85 mph speedo markings.
Going one way, you'll be off 15%, and the other, about 7%. The only
other way to do it is to have the speedo face recalibrated and screened
by a VDO repair center.
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