Here's a couple of Ebay links to order the coils
at the best price that I have seen so far($29.99 each).

Here's the Ebay link for the 12" coils....
12 inch


Here's the Ebay link for the 14" version....
14 inch

3" lift is common on the usual saggy Runner using the 12x125 coils.
4.5" lift using the 14x150 coils.

Pick-ups don't seem to sag like the Runners. They also seem to have a larger
distance from leafpack to underside of frame so the 14" coils are a better
choice for them.

Some saggy Runners have 3 or 4 inch blocks and longer shackles to get lift.
The 14x150 coils will allow the blocks to be removed with a wonderful 
soft ride. Even the long shackles can go away.

It's best to get out the jack and measuring tape to make sure things fit
and won't "fall out" in the future. Jack the rear of the runner with tires
nearly off the ground and measure the spot where the coil will be. It 
should be less than 12" meaning you can safely use the 12x125 coils. It
also means you can cut the upper steel stopper to 1" in length. This lets
the coil slip right in with no hassle....no torching, bending, or strange
coil noises. 
A sawzall will cut the stopper very cleanly. Mask off the area to cut and,
done right, it can look like it came from the factory that way.