Paul,
As i know you need to put the whole cluster in it.You coult try to chance the speedo with your encoding plug.With the encoding plug from a US car it schoult be working.The only thing is that the oil temp is working like a tank meter.
I put one in mine and i had to chance the whole cluster.It was the only possible way.Otherwise it schows 210 kmh by driving 120kmh.Including the M5 encoding plug the oil temp was working.But i needed the original km so i put my 525 plug in it.Now i am driving with oil temp witch is working like a fuell meter.
I hope this is what you like to know.
