rangers werent supposed to get flex fuel until '99. as well as the tailgate symbol, you can check your 8th VIN digit..FFV is V.
to convert your truck to flex fuel...you sell it and buy a flex fuel truck. if you were to try to convert your truck, it would involve a complete fuel system swap (tank, lines, ethanol sensor, injectors, and associated gaskets and o-rings), MAF sensor, and computer.
i wouldnt get too hot and bothered about E85 if i were you. it sounds OK on paper, but in practice, most people dont break even by running e85 (E85 doesnt provide as good of fuel mileage as regular gasoline).