Converting to run E85 is relatively easy. Simply change the injectors to approximately 25% larger ones. Dump in the E85 and go.

If you want to get fancy you could recurve your distributor (if so equipped) for better power and mileage. Edit: Your '91 probably has computer controlled timing, so you'd be out of luck there unless you went with an aftermarket ignition and a duraspark distributor or something like that, or found another way to change timing.

It gets a whole lot more complicated if you also want the option of running gasoline.