Shocks....Confusion

I just picked up a 3.5" RE Lift for my XJ. I hear they net around 4 to 4.5" of lift. Plus I'm adding a 1" Spacer. The rear, Most likey will be a 2" block. So what size shock should I go for? Someone with some experince should know!!! Where is the best place to get shocks cheap? I dont need anything Fancy...This jeep will be towed 75% of the time to the trail.

Thanks Yall!
Rick