Pac Brake's application guide
https://pacbrake.com/mm5/pdfs/PRXB-Exhaust-Brake_Guide.pdf indicates that for automatic models with a standard exhaust and turbo elbow (thus a 4 inch direct mount system) and
owner provided onboard air, there is a different kit for each of the following.......
2003-2004
Cummins 5.9L ISB 24 Valve Engine - 47 / 48RE Auto Trans (Built up to Jan 4, ‘04)
https://pacbrake.com/C44032
2004½ Cummins 5.9L ISB 24 Valve Engine - 48RE Auto Trans (Built Jan 5, ‘04-Jul 25, ‘04)
https://pacbrake.com/C44033
2005 Cummins 5.9L ISB 24 Valve Engine - 48RE Auto Trans (Built up to Jun 27, ‘05)
https://pacbrake.com/C44033
Note that the last two are the same kit..... in both kits, C44032 and C44033 a transmission controller is included with a special toggle switch with an illuminated handle that displays red/green/yellow to indicate the status of the transmission and brake.
The 2006-2007 kit: 2006-2007 Cummins 5.9L ISB 24 Valve Engine - 48RE Auto Trans (Built after Jun 27, ‘05)
https://pacbrake.com/C44037
Does not include a transmission controller nor is one needed, as the factory transmission computer controls the transmission lockup functions when the Cummins computer activates the EB. This is the same kit as 2004½-2007 straight shifts with a simple on-off toggle switch to operate the EB. 2003-2004 straight shifts have the same kit but a different brake valve due to differences in the down pipe.
The OP can install a compressor using a mounting bracket and compressor from Pac Brake or ARB or one or two other sources, so long as the air is controlled by ignition power so the air is available when the engine is running. This compressor installation is not difficult, just requires a little creativity.
I installed the engine mounted compressor, for ease of installation, but may someday install a larger frame mounted compressor, which will require a fair amount of re-plumbing and re-wiring. I just wanted it done so I took the easiest route.
Pac Brake air compressors, brackets and components can be found in the
https://pacbrake.com/mm5/pdfs/Air-Suspension-Controls_Guide.pdf I still spent a fair amount of time on Amazon looking for fittings and tubing as I mounted air outlets on the back end of each running board and that the air tubing supplied in the kits was unusable and trashed it in favor of SAE J844 marked air brake tubing.
Charles