5.9 No emmissions BS, the 6.7 has EGR DPF.
5.9 is a little bit better on fuel economy.
- 2003, 2004 you could get an NV4500 5 speed behind the standard 5.9
- 2003, 2004 the NV5600 six speed came with the HO version
- 2004.5 early 2005 The NV5600 was standard, no NV4500 offered, no longer...