Hi Dennis - to the best of my knowledge, seat selection is only possible with Trenitalia themselves, who charge a €2 premium for it. Unfortunately though, they no longer sell Eurail reservations online, but you could probably make specific seating requests when booking in person at an Italian station.

Of course, wherever you do end up buying - OEBB, Italiarail or Interrail - you can still consult your tickets afterwards and see your carriage and seat numbers, then compare them with the seating plan from a dummy booking of the same train at trenitalia.com, but this is something there would only be any point in doing out of pure curiosity, as you wouldn’t easily be able to change what you had if you didn’t like it...

Oh-the panick again-there is no real need to make all those REServations for the normal daytime trains-that often run ev. hour on main routes, monthes or even longer in advance. Its not that you are scrambling for the very cheapest air-tickets. Just take an hour or so (Yes, I know, an awful prospective for many a USAer) on the first major stop in IT and go to counter and find the /en/ person and have them your wishes fulfilled. And be a bit flexible-if the 8.55 is not available on your favored seat-then take the 9.55. or take it is that is really way out of the question