I'm going to go with you having a gasser not the diesel. Either the nv3500 or 4500 will work in your truck, the 4500 is a heavier duty trans and in my opinion is required if you're going to tow much, the nv3500s just weren't built for it.
For the NV4500, people think they are worth their weight in gold, but you may be able to find them cheaper by looking in chevy sale forums as the NV4500 had an interchangeable bellhousing, then all you'd need to find is a ruined nv4500 out of a dodge and get the bellhousing.
For the conversion, you'll need the pedal assembly (the whole thing, the clutch was not separate), the master and ***** cylinder, drive shaft, trans mount and shift column if it doesn't come with the trans.
Also, if you have an auto now and you swap in a manual it will **** off the PCM and throw constant check engine lights at you, im not sure if the torque management will still be in effect, though I don't see why it wouldn't. The only fix for that is to get the PCM tuned/flashed or get a PCM from a 97 or early 98 with the 5.9 and a manual trans.
