Thanks for posting all that! Now I can drive around with my speedo working again! :laugh:I swapped in a Scirocco cluster when I did the 16V swap into my Caddy.
The procedure is not the same for all "Mk1s"- A later german built A1 Cabby or Jetta will be an easier swap due to mounting and clearance issues...
But since your sig says "83 GTI" you have essentially the same issues I did with my pickup.
Speedo cable- You'll want to use the one-piece speedo cable from the A2 Jetta diesel. This will allow you to get rid of the box in the raintray. The hole the cable passes through- interior side of the firewall will need to be enlarged in order to clear the larger diameter (and slightly different angle) of the clip on style cable retainer. Failure to grind for clearance will result in a "ticking" speedo, followed shortly by a broken cable- don't ask how I know...The lower right side of the hole is where you'll have to grind out.
The 16V cluster mounting arrangement is totally different from the Rabbit GTI cluster as well. You'll want to grind off the round mounting posts on the sides and the top bracket of the 16V cluster. I made new side mounts from 1" angle aluminum- cut to fit- then used a hidden pop rivet and weatherstrip cement to secure them to the sides of the cluster. This will hold the nacelle steady- some people just stuff the cluster in there and hold it in with the faceplate- but any shifting/vibration will eventually mean trouble. (As mentioned later)
Wiring: You'll need the Bentleys for the GTI and the donor car. I thought I still had the cross reference chart here handy, but a 20 minute search didn't find it. Be sure to solder and shrink your connections. A minor issue is the Scirocco cluster does not have the LED for the parking brake. I used the LED for the OXS instead, and made another icon with my scanner and a printer. The MAJOR issue is you are going from a single plug harness to a dual plug harness. Here is the hardest part of the whole conversion- what to do about that left hand plug that happens to hang down into the steering column brace. I've heard it is possible to grind enough material off the brace to clear, but that idea didn't appeal to me. So I used the method suggested by Chris (Caddy 16V)- unsnap the left harness connector from the cluster, spin it 90 degrees then tie wrap it to the column brace. This is why you want the cluster secured by brackets- if you don't secure it, the edge of that brace will act as a saw on the foil that links the harness to the cluster- eventually causing problems. Be careful when you route it-a wrap or two of electrical tape around the foil wouldn't hurt either...
It is a bit of work to do the conversion, but it's worth it to have that 8k tach!