DO U NEED THEM OR IS A SHACKLE GOOD TO

I have used both and sliders work better all around.

The problem with using (2) shackles is that the rear end shifts all over the place in the corners and through ruts.  You need to get the hangers down a little to get some decent lowering blocks in.  The SS that do use shackles only use them on the LR. The RR slider locates the rearend as the LR shackle unloads creating more bite on the LR.