I wanted to 'try' to get into an 04-05' non-flex for having the most common ECM, injectors, and returnless fuel system while still being DBW...(while not really important... it did save me $$$$ with not having to run 2 sst braided lines up the chassis from my rear mounted tank vs. returnless
SOME IMPORTANT INFORMATION regarding 5.3L vortecs
Injectors (non flex)
PN 25317628 2001-2007 - 4.8L, 5.3L, 6.0L - flows 3.180 gm/sec or 25.2lb/hr @ 58 psi
03+ throttle body: 8 pin connector on passenger side only
tac module: 99-02 all plastic, 2003+ plastic with metal mounting bracket
VERY important to do your homework (or get all the stuff from the same truck) regarding gas pedal, pedal TCM unit, engine ECM itself, the potential wiring harness uncut if possible... otherwise you REALLY have to pay attention to making sure your sourcing components that play nice from the correct model years.