Do you mean the transducer?

I take it youve tried the red button on top of the dash?

theres a selection of speedo drives for these:

1 TRANSMITTER,DISTANCE 1 90148828 12 36 262
FREQUENCY,6IMPULSES (IDENT AA)
Note: USED WITH MANUAL TRANSMISSION
90148828

2 TRANSMITTER,DISTANCE HATCH 43,44 1 90149083 12 36 267
FREQUENCY,6IMPULSES (IDENT AH)
Note: USE WITH LCD INSTRUMENTS
90149083

3 TRANSMITTER,DISTANCE 1 (90149084) (12 36 268)
FREQUENCY,7IMPULSES (IDENT
AJ) (NLS.)
(90149084 )

4 TRANSMITTER,DISTANCE 20XE,C20XE 1 90149082 12 36 264
FREQUENCY,16IMPULSES (IDENT
AG) (USED WITH TRIP COMPUTER)
Note: USED WITH MANUAL TRANSMISSION
90149082

5 TRANSMITTER,DISTANCE 1 90185189 12 36 271
FREQUENCY,16IMPULSES (IDENT
AK) (USE WITH LCD INSTRUMENTS)
Note: USED WITH MANUAL TRANSMISSION
90185189