Correct. The cluster housing/printed circuit is completely different than earlier because of that, and also the "deletion" of the old clock/tach gas gauge location. (It's there, but set up for three idiot lights...no mounting tabs for a gauge, and to even fit a gauge, you'd have to dremel a bunch of the internal ribbing out that separated each area for the various lights they could have used there.)
Your comment about the ribbon cable connection is one of many reasons I removed the printed circuit and hardwired the whole cluster.
Those gauge cluster package I posted from Digital Dakota may not work with the odd ball 90-91 trucks. They list the 91, but they may not know what they are talking about. I can see hard wiring all the gauges, but what light sockets did you use to hard wire the dash socket bulbs?