As you can see, there is a difference of opinions, depending on kit type, wheeling style, and comfort with rubbing.
With the 2.5" lift, extend your rear brake lines. No exceptions. The redneck solution (I know, because I considered it
) would be to simply pop out the retaining clip from the frame and release the stock bracket from the frame to give you extra available length in your brake line. But then your line is just flopping around and could easily get ripped out on a rock or branch. Therefore, buy brake line extensions (the lines themselves, or the bracket extensions, or fab your own extensions--I have done this before with a $3 cabinet bracket from Home Depot).
Bumpstop extensions: take 'em or leave 'em. If you put them in and you continually pound on them, you are putting stress on your front frame crossmember--I have seen some of these crack over time, but mostly on regularly abused Jeeps with springs starting to fatigue. If you DON'T put them in and you wheel hard with 35's, you could risk ripping a flare off. Boo-hoo. I don't use them, for the most part.
Are you running your factory rims? If so, leave the stock rear links on, and spend $50 to buy another set of rear links from the dealership to use on the FRONT. If you are running aftermarket offset rims, or wheel spacers, then do what the kit says and use the kit long rear links, and put the stock rear links on the front.
You didn't ask about a rear track bar relocator or whether you were going with shock extensions or buying longer aftermarket shocks, so I won't go into that.