You shouldn't need an adapter kit if this is the right factory radio for your 91. The kits like you see at Walmart are intended to connect an aftermarket radio to the Toyota factory connectors already in the dash. The wiring and it's connectors to plug in to the factory radio should already be in the dash. Look around under the dash for them. Someone can correct me on this if I am wrong.
In addition, I believe the correct part number for the radio you have is 86120-12850.
Mike
In addition, I believe the correct part number for the radio you have is 86120-12850.
Mike