It's been covered here a lot but the search will take some time for a new guy to learn. So in other words it's covered in detail but here are the Cliff Notes:
"Easiest" swap is the somewhat rare 1991 needle cluster. Not all 91's came with it. It has the same connector your 90 has, though you will need to move 3 wires around in the harness connector for it to work right. You will also likely need to recalibrate it for your gear ratio/tire size unless you somehow get lucky and get one already set right. They can be hard to find - that's why quotes around "easiest" ...
Next up, 1992-1994 cluster, can be installed but requires you to change out the harness connector, wire in the DRAC module, and hack the plastic a little bit in the back of the dash behind the cluster so the connector will fit - also not really a perfect situation as the depth of the area back there is a little different so the connector isn't supported well.
Finally, spend huge money on an aftermarket cluster like Dakota Digital has a couple options but they're $$$ and don't forget to add in all the senders you need to support it.
Richard