Black Bear Performance does a good job tuning. I purchased an autocal from them, and had my 2014 GMC 1500 tuned. Noticeably improved driveability- better shifting, and the reduced torque management makes it feel more peppy. Cost more than a run of the mill programmer, but it's totally custom to your truck and the mods you've done. With where you're headed performance wise, I'd definitely recommend a tune to make the most of your mods. You've got a sharp truck!
I don't know the Chevys very well, but I personally wouldn't be running those mods without a tune to compensate. You could very well be running lean and the PCM can't figure out what to do.
Bilstein 5160 remote reservoir shocks are cheap, but they don't hold up the best to salty winter weather. They had 3 different lengths, so you could probably find the ideal compressed and extended length for your truck. Generically tuned for half ton steel trucks as far as I am aware.
Bilstein #25-242515 (Reservoir) allows for up to a 2" lift
Icon #76526R (Reservoir) allows for up to a 2" lift
Fox #210-90144 (Reservoir) allows for up to a 1" lift
Pro Comp Pro Runner #EXPZX3020 (non rezzy) allows for up to a 2" lift
Icon #76526 (non rezzy) allows for up to a 2" lift
Fox #980-24-660 (non rezzy) allows for up to a 1" lift
Bilstein #33-238319 (non rezzy) allows for for up to a 1" lift