If you do remove the instrument cluster, make notes on which colored wires go where. Else you may be writing on this board again, asking for wire locations.

And most importantly, there is a red and white wire that is only to be used for a tachometer. It's there even if you have no tach, but will destroy anything else to which you attach it. BTDT. It carries high voltage from the coil, which is why it can be so destructive. So tie it up, maybe put a label on it "TACH ONLY"

Oh yes - here's a tip, if you do pull the cluster.
If you'd like a bit brighter illumination in there, get some aluminum foil and contact cement before hand. Open the cluster (7 screws on back at corners & edges). Now you can see the 2 illumination bulbs - remove them carefully and gently, without getting fingertip oils on them. Line the little "reflector" housings with trimmed aluminum foil, glued down. You'll find white plastic that's gone dull yellow, and maybe also some black plastic that can become reflective if you line it with foil. Don't let any get too close to the socket or the bulb. Insert bulbs carefully; they cost nearly $10 each. I did mine ('89) at least half a year ago, that's 25-30K miles, and no troubles since then.

Good luck!
--
Sven: '89 245, IPD sways, electric rad. fan conversion, 28+ mpg - auto tranny. 850 mi/week commute. '89 245 #2 (wifemobile). '90 244 (spare, runs).