I have done the conversion to my vr exective which have the same setup as yoursThe digital bottom section of the dash will not work it needs another connector called connector number 4.All the speedo,tacho,fuel,temp and most idiot lights will work OK .
You need to source a cluster harness to suit a digital dash from say a berlina or statesman or calais from a wrecker about $40 -50
This harness goes from the 3 connector boxes located on the side of the dash pad on the right hand side to the instruments taking in the cluster , heated window...air con...hazard switches and glove box light.
You need to use the connector 4 from this new loom and solder a few wires to existing wires in your original dash loom.
I did it and the dash works perfectly.
If you are keen I can send you a diagram.
Mark.