It will work fine in the 03. The 04. 5 will work also, however it may possibly cause the catalytic converter to stop functioning with time (meaning you possibly wouldn't pass a smog test, it won't affect the truck otherwise)...
The CI was the older designation, and was upgraded to CI+4 when the 04. 5s entered the market (less additives that can harm the catalytic converter). The CJ-4 was introduced in 07 (?) for the Diesel Particulate Filter (DPF) equipped engines.
Personally, I've ran CI in my 04. 5 before; mainly because the oil hadn't caught up to the truck sales at the time... and if you need oil, you use what's available. My kitty ran away a long time ago, so I never worried about the CI/CI+4 thing.