Not speaking from first hand experience here, but as far as I know you just unbolt old and fit new. I think it still takes the standard speedo, tacho and other inputs but plays with them internally to give a digital display, not an normal analogue one.
Also try talking to the MA70 Supra boys, imports had digital dashes and ADM had analogue. Someone will have swapped. And they're from around the same period.
Hen