Turns out depending on whether the car was equipped with TCS or not there are different signals coming to the dash, meaning there are different speedo clusters.
Wired in a speedo calibrator box from aliexpress and now works fine.
Did You get the speedo working? Was it the cluster?
Mine showed nothing until I wired it straight to the speedo. Then it read 10x lower. Changed the clusters - now reads 5x lower speed
Not much information on the net for r34...