At work a few years back we had an AE86 with a digi dash and after getting it repaired three time six months apart at about $300 a shot I fitted an analoge dash. The wiring is different and you will need and oil sender as you will have a light and AE86 analogue have a gauge and the fuel senders are different.
But I have done it and it is possible!
Took me about 1 hr to change the wiring to suit. And then all the other stuff.