99 f150 lowered 3/4 shackes and hanger in back

now if i get a 4 degree shim do i just put the truck on stands jack up rear end, unloosn the u bolts and slowly let the axle down so i have space to slap in the shim??? then jack up axle line it up and tighten it down or does the shim go between the acutal leafs?

do i need a longer bolt to go threw the leafs?

anyhelp is apprecaited

 

it goes in between the axle tube and the leaf spring pack, make sure you put it in the right way, good luck