On the sticker on the under side of the hood, the reason it only has 3. 5 stated on it for the axle ratio(s), is that the 1500's had a ratio of 3. 55 while the 2500 and 3500's have the 3. 54's. I guess they figure 3. 5 was enough for most, since a lot of people (non-gear/diesel heads) don't even know that sticker exhists.
BTW, they have since moved that sticker on some trucks to the glove box.
Ben