So I already have the keys up front? What's the point in buying different ones? Now for the back I found a lot of coil spacers that said for front only. I believe it was the Daystar spacers from topguncustomz website.
Daystar are polyurenethane and are for front coils. They are not what you need. Get either the ones I sent links to, suspensionmaxx or McBay Performance website. Just search for rear coil spring spacers. There are tons online to buy. The link showed you before from ebay, that guy has all set ups and the price is very good.
The keys up front are stock. They only allow you to gain about 2" tops depending on how badly your bars are sagging. Buying aftermarket ones or ford keys will allow you to gain more height because they are reindexed (2.5-3.0"). This is a good read with lots of information to answer most questions on cranking torsion bars
http://www.gmfullsize.com/tech/torsion401.html
Lastly, don't waste your time on the Rough Country level lift either, many are very unhappy for the price. The keys do not give as much as ford keys...cost much more, and the rear spacers are .75 poly.
There are many threads on here about options on how to lift, brands that were ran, and end results/measurements.