2008 Taco DC weak leaf springs

I sense some confusion going on here.

Coilovers are for the front of the truck. not the rear.

The rear of these trucks use leaf springs. Without fab work you will not be able to run coilovers in the rear.

I suggest either getting the firestone airbag kit and keep your current leafs or replace your leaf pack with something like this

Then you will need new shocks to go with the leafs

or if you're trying to save cash then go with an add a leaf, you should still get new rear shocks.

 

This^^
He laid it out for you real well here.