Ya, I had the 255/70R16's also... the 31's are very close in height (maybe 1/2 inch taller at most), and are a bit wider. I like them because it didn't throw off my speedometer at all.
With the 8" wheels and less backspace, they stick out more so they look a bit bigger. And it's definitely a rougher ride with the All-Terrains vs. the stock tires.
Here's what it looks like:
As for the 32's, I think they will fit with a T-bar crank. If you search, there are posts that say they will fit without any changes and others will say that you need to crank the t-bars or they rub a bit....