I dont know of any fab shops in or around CO that you could use, but as far as springs are concerned there are several companies that make very high quality custom coils and leaves. Deaver spring, Atlas spring, and National spring (in that order) are the best as far as their products go. Another question would be if you are going with tires that are so large that you need to move the axle forward more than 1". Most aftermarket control arms can handle 1" forward, but if you go any further than that you will need custom arms and you run into problems with the coil buckets/shock towers needing to be moved as well. My recommendation is to see what you can tuck in the fender, and cut (cleanly) as much as possible to keep the truck low, like in the 4" lift range. Im guessing that since you bought a 5500 it will be heavily loaded and the lower CG is important. The rear is usually a non-issue and only requires springs and shocks. If you were in Cali I could recommend many good shops to take care of your fab needs.