The odometer on my recently purchased 1985 300TD-t only shows about 80% of the actual mileage.

I know that it is *not* the original speedo.

it currently has a 150MPH speed o that shows ~ 58mph at 3000rpm
( if my calculations are correct, when i show 58, I'm doing 72..unless I'm cracked)
a 'spare' 100mph speedo, along with the 85 mph one from my 1982 240D both show ~ 54mph at the same RPM.

I've found the parts numbers for proper replacement speedo's
(per EPC online seems 85mph and 125mph versions are available)

*o.k. to the point!*

teh parts numbers i have are:
a 009 542 67 06 ( 85 mph)
a 010 542 75 06 (125mph)
a 011 542 68 06 (125 mph)
(along with some others that "are replaced by" newer part numbers such as those above)

the parts numbers that i *SEE* on the speedos are written as:
123.542.37.01 (in the case of the currently installed one)

how do i cross-reference these? (is it as simple as ignoring the leading set?)

I'd hate to spend money on another unit designed for a different rear-end-ratio.

thanks!!

Robert