It is not generally correct to say that no parts are different between FF and non-FF vehicles, IME. There are exceptions, of course, but typically the non-FF vehicles do not have sufficiently large injectors, such that when run on alcohol (E-85), and assuming the ECU is re-programmed CORRECTLY (highly unusual, again IME), the injectors cannot keep up with demand. This means they're running at 100% duty cycle, which dumps fuel at the wrong time, and yet still results in too-lean AFRs. Driving around town it's often not an issue, but pulling a load, driving up big hills (mountains), and things such as that will cause trouble. It is common to have to replace the fuel pump, too, again in order to be able to deliver sufficient fuel.
The domestic brands may well do a better job 'universalizing' parts between FF and non-FF vehicles. They push alcohol much harder than the Japanese makes.
I've run E-85 in a non-FF turbocharged Japanese vehicle for a couple thousand miles before, in which I already knew the injectors would flow enough fuel, but which needed new fueling maps (and also really needed a new fuel pump, or at least a different Fuel Pressure Regulator). It ran fine most of the time, but it would not idle when cold, and it was significantly too-lean under WOT operation, even at altitude. I also had some o-rings in the fuel rail go south on me a year or two later. Probably coincidence, but possibly not. That failure resulted in raw gasoline being leaked out over the top of the engine. It was not the best situation I could have thought of/hoped for.
In short, my experienced opinion is that, IN GENERAL, you're unlikely to cause significant damage or problems from throwing some E-85 into a very late-model vehicle once, particularly now that E-85 may have as little as 51% alcohol in it. That said, you're not saving anything at all, leastways the environment, and you _may_ cause significant damage to some components over time.
