I did this conversion to my '83.5 (AND did it without JB Weld). The 14-pin
connectors are the same, but the order of the wires are not. I HAD a diagram
I had made from the Bentley but it is missing. The two different socket
orders are pictured, all you have to do is gently pull the wires out of the
connector and reinsert them in the new order. You will be missing the circuit
for HIGH oil pressure. The low oil pressure sensor works. I had to add a wire
to the coil for the tach.
The guts of VDO tach/oil/fuel cluster is essentially the same as the one used
on high end Rabbits and Jettas of the same vintage, the main difference being
the housing on the back and the redline on the tach. These can be inserted
when the tach or temp gauge go bad, as they are prone to do.

Scott
'83.5 Vanserai