It sure sounds like a bad CV. Get under the truck grab the axles, shake the hell out of them and compare the movement between the two. I bet one has more slop than the other.
I threw some rebuilt axles in my kid's GTI a few years back that made almost as much noise as the bad ones I pulled...
NAPA carries factory rebuilt axles, but not everyone one they sell is. I'd compare before installing. I've got about eight months and some pretty rough trips out of them with no issue. That's the route I'd go.
I used the one on Bell and 35th for a number of vehicles without issue. Heck I had an LR3 aligned first with the air suspension then six months later after a coil conversion, and not a word said. Just make it clear an alignment is all you want because you do all your own work, and they should...
The platform sits on the spare tire.
The spare is mounted in the truck bolted to the floor. The platform sits on top of the spare and is bolted to the spare via a coupling nut and then two smaller bolts on the bracket.