Do you ever plan on lifting it? Spindle lifting it? If so, I would suggest 31x10.50 or even 32x11.50. But if you need tires badly now, go ahead and get what you are already thinking about. I would even suggest something like a 235/75R15.
Tires still stick out past the flares a little bit...not much because you're only going with a 9.5. And honestly....9.5 on an 8....the rim is a little too wide for the tire. 7" is perfect for a 9.5 or 10.50 tire....8 is perfect for a 10.50 or 11.50 tire....another reason to bump it up to 31x10.50.
Stock spare will work just fine. You are not locked in the back, and even if you are limited slip, different tire diameters are perfectly fine.
Speedometer be off......hmmm....what size is your stock tires? You're speedo should read about 1-3 mph slower than you are actually going.
Mpgs shouldn't be much of a difference......the way you calculate mpgs will need to change though. With the speedo showing and reading slower, this also slows the odometer as well. My truck with 4.10s and 35's when it came stock with 4.10s and 30.5's, the difference was 10%...so my odometer says 100 miles, I actually went 110. Figure out your difference andyou'll be fine. Generally, you'll get worse in-town mpgs, and better highway/freeway mpg's.
'01 XLT disguised as a '03 Fx4 Level II
Big. Loud. Slow. Bright.