YJ brake lines are longer than XJ brake lines, both front and back. You can get stock YJ brake lines from any parts house, either side in front and the back one, and bolt them right up on the XJ. I also heard that S-10 brake lines are even longer than YJ's.
Personally, I don't like stainless steel brake lines. I've seen many, many brake lines break on the trail, and they've all been stainless steel. There's no give, or stretch, like in a stock rubber line, so if they get pulled or snag on something they come apart. Also, stock lines are cheap and easy to replace, and it's inexpensive to carry a spare.