I did a 16V Scirocco cluster into an 84 Rabbit dash. It mounts to the dash a different way, had to fabricate mounting ears. Also had to clearance the connectors around the steering column. I also used the complete 16V wireing harness in the Rabbit, since it received all the other parts from the 16V. Had to splice the lighting wires to the Rabbit lights.
Friend put the 16V dash in his Mk1 Scirocco and used a 16v cluster also for his 16v Scirocco. There was some cutting to fit there also.
where there is an insane will, there is a way. If it don't fit, make it fit. be able to fabricate.