Is there any particular place you'd recommend for a cheap NOS kit?
Take a look on eBay. I think what you'll want is a "wet" fogger type system, with a single "Fogger" nozzle, 10 pound bottle, fuel & nitrous solenoids, hoses, mounting for the bottle, etc. I'm sure you'll want a remote bottle valve/solenoid for it too. You'll probably want to start with a 50 HP "shot". You can always re-jet for more HP. If you're at all good at fabrication, it should be easy to install; you won't need an application specific "kit" for your truck. As for the brand, it really doesn't matter, but since they've been around forever and make all the goodies you'll ever need, I like NOS brand. Pick what looks good to you. I'm sure you can gather up everything you'll need (new) for under your $700. It was a few years ago now, but the last "kit" I bought used, cost me $200 for everything (4 barrel plate system). Lastly, READ UP on nitrous before installing & using your new HP!