replacing leaf spring bushings

[nation]

today i found out i need to replace my leaf spring bushings. im not sure what brand lift i have(i think its pro-comp)
does anyone make a poly bushing for the rear? do i have to replace the shackle?
for the front will the bushings only work on certain suspensions?
here are a few i found

for the rear
Pro Comp Suspension Systems 90-3806 - Pro Comp Leaf Spring Bushing Sets - Overview - SummitRacing.com
for the front
Energy Suspension 4-2148G - Energy Suspension Leaf Spring Bushing Sets - Overview - SummitRacing.com

or would this kit be the better buy
http://www.riffraffdiesel.com/mm5/merchant.mvc?

[RichardT]

I know when mine went out. I had to get the Fab-tech bushings, because thats the lift i had. And at the time Fab-tech was Just getting back in buisness. So i was having a real hard time finding them and its not fun installing either. I ended up taking the leaf spring off and having them pressed in.