If I were to put a 6.5" longer shackle on my rig what would i need to change? ie. longer brake lines. I already have a 3" suspension lift.

 

you wouldnt have to but if you do a lot of wheeling I would mine were streched past limit with a 4.5" lift I bought trail-gears brake lines and they were awesome paid $69 for the set of 3 + shipping and its a good investment to me. better safe than sorry

 

If you were just putting the shackles on it would be fine but since you have a 3" already I would say extend them. another tip for the front is to bend the tabs that the top of the rubber brake lines are connected to in towards the tire instead of back towards the back like they are stock. Gives a bit more play.

 

I run 3" downey leaf springs with 5.5" shackles and I don't have any issues. The only issues I've had with the longer shackles is that I had to extend my bumpstops. Before I extended the bumpstops I found that when I flexed my rear leafs inverted, which I imagine couldn't be good for the life of the leaf springs.

 

Is this a 6.5" longer than stock shackle or 6.5" longer overall or center to center?
- http://www.4crawler.com/4x4/ForSale/Shackles.shtml#FAQ4

You may need shims to correct pinion and caster angle changes along with the above noted items:
- http://www.4crawler.com/4x4/ForSale/...es.shtml#FAQ12

 

6.5in center to center