Engine year

Also, the '04 does not have MDS whereas they added MDS on the '06 models. You really don't need MDS on a hot rod, but it could be eliminated on the '06.

Another tid bit tough, if you can get the ECM and harness on the '04, it's pretty easy to use it in your hot rod with any tranny. The ECM on that model year was stand alone, not integrated in with the TCM as the '06 would be. (assuming both trucks are auto trans)