It's not that easy of a switch, You should use a new analog wiring harness cause the pin out diagram for those two dash's are completely different and the Fuel level power is different, the fuel sender on a digital dash has different OHM's and More!
Not an easy task to say the least. Way more hassle than it's worth going from a stock digital dash to a stock analog dash if you ask me cause in the end you still have stock 1987 technology.