To give you an idea how Tire Rack can usually deliver in a day, look at...
That'* the main warehouse in South Bend, IN. It'* FULL of tires and wheels.
If you've had good luck with your OEM tires and want the same tire, you'll probably be disappointed. Aftermarket tires of the same brand/model are usually a different compound and will behave differently. Learned that from hanging around Ford engineers. I had a set a Goodyears on my 1991 Bonneville that went 80,000 miles. I replaced them with same and only got 40,000 miles.
If you're playing around with tire sizes, you will want to make sure you get the same OD. I recall that the Tire Rack has a tire calculator to check sizes. If not, there are websites that have calculators or you can download my Excel program from MIFbody.com:
(scroll down about halfway)
The calculator will also give you speedo error. For example going from 235/55-17 to 255/50-17, your speedo will read 70mph, but with the new tire size, you'll actually be going 0.4mph slower than before. (OK, big deal!)