A good set of injectors for that truck will run upwards of 2300 dollars. The stock injectors are usually good for around 400hp depending on what programing you are using (chip). Like I said above, guages first, then intake and exhaust, then a chip and then the big dollar stuff like pumps and injectors.
You don't want to just throw a set of injectors in an otherwise stock truck as it will create problems and reduce the longevity of the engine. First you need to have more air in and out which an intake and exhaust kit will do. The chip will also bump the power up and will be ready when the injectors are installed.
You might want to check out Dynomite Diesel Performance and DSP, both companies have really good injectors. I'm not sure if they have a website, but H&H Diesel Service is Fife Washington has been doing custom high performance work for me for a number of years. They just finished a pump and injectors for a Big Cam III Cummins I'm working on. Also, Industrial Injection Service in Salt Lake builds good stuff. I have a set of HEUI injectors from them I'm running in my pickup. I've used both H&H and Industrial and have been happy with both outfits.