I believe the JK Rubicon wheels are 6.25" of backspacing on a 17x7.5 wheel. Your Sport TJ has the narrower 3.25" flares, so it shouldn't be too difficult to extend past the flares.
A 1.25" thick adapter would give you 5 inches of net backspacing and bring you to about the track width of a TJ Rubicon. You would probably end up with about 1.5 inches of stick out. Larger spacers will give you a wider stance.
Spidertrax adapters are hub centric on both the mounting side and the adapted side, and are made in the US.
http://www.spidertrax.com/Jeep-JK-Conversion-Adapters?sc=2&category=9998
As a basic guide, a TJ body without flares is 59 inches wide. Non-Rubicon/Sahara flares are 3.25" wide, Rubicon/Sahara are 4.25". So the covered width of your Jeep is 65.5". A stock TJ axle width is 60.5 inches.
So with 1.25" spacers, the wheel centerline is going to be 1.125" inboard of the wheel mounting surface. 265 tires are roughly 10.43 inches wide, so the net width of the axle and tires in this case is 68.5". So you will get 1.5" of stickout (measured from the sidewall of the tire) from 1.25" spacers.
I wouldn't recommend exceeding about 1.75" thick, because a wider stance will adversely affect steering geometry due to the change in scrub radius.