I installed a 3 inch rough country suspenion lift and 31x10.50 tires.
now when i reach about 50 mph the front end shakes so bad that
the front tires bounce high enough to bark when they hit the road
again. (kinda scarey to drive now lol ) But if anybody might have a
clue to what causing my trouble i would greatly appreciate it

thanks in advance

You need to install an adjustable track rod and have an alignment shop re-set your "king pin" inclination back to the stock specifications.

Heres the one that goes with but does not come with your lift kit.
http://rough.roughcountry.com/84-01%20Jeep%20XJ.htm

Also have your tires re-balanced. Some times tire stores just don't get it right the first time with large tires.

it is called bump steer a proper wheel alignment should help

I installed a 3 inch rough country suspenion lift and 31x10.50 tires.
now when i reach about 50 mph the front end shakes so bad that
the front tires bounce high enough to bark when they hit the road
again. (kinda scarey to drive now lol ) But if anybody might have a
clue to what causing my trouble i would greatly appreciate it

thanks in advance
You have the 'death wobble blues' and is a common problem with lifted XJ's that have a few miles on them.
The previous suggestions are good and you must be sure that the ball joints, tie rod ends, drag link and steering stabalizer are good with NO looseness or excessive wear in them.