Re: 03-04 shocker?
post 03 shockers are all referred to as 03 shockers. After the 1st 2500 shockers, Smart Parts worked out any little bugs and corrections on the basic internal design (and by changes I mean material used to construct the bolt guide, the on/off switch). In late 04 early 05 they introduced the nerve board with ramping modes to the shocker, same as in the nerve marker. So far all intents and purposes all post 03 shockers are the same, only question is what board is in it.
I hope this helps, and for one last piece of input, I love my shocker. I keep adding little tweaks to squeak out that last bit of efficiency. You will definitely want to invest in a high efficiency bolt, beyond that they are great even stock.
Best of luck - Smoke, aka Mark