Ya know, I kind of wish that they did the opposite. I'm all for freedom to modify vehicles how ever you want to as long as its safe. Forget emissions inspections, but do some general safety inspections. The amount of vehicles that I see running around this state with glaringly obvious safety equipment failures is astounding. Stuff that onlyl puts the owner/operator at risk, what ever goes. Stuff that puts others at risk, no-go. No seat belts or sitting on a milk crate, who cares. No working brake lights (or lights at all) no brakes, not acceptable. Problem is, if we start letting them do that, who makes the call on what is safe and unsafe. That whole give them an inch and they'll take a mile works both ways.
As for your truck, you don't need anything from the state. It might get funny looks, but it's perfectly legal anywhere here. Even if you had a letter from GA saying that it's roadworthy, another state isn't going to care what GA thinks.
What's the deal with the camper? I don't understand the question there. Doesn't matter that it's only a single axle. They don't need to see the title, just that it's registered which they can easily get from running the plate. Is it no longer a pop-up and been converted to something else? As long as the serial number plate matches the registration all is good. Converting old pop-up frames, camper frames in general, into utility (or other) type trailers is a common occourance everywhere. My 6x14 (IIRC) flat bed was formerly a camper frame, though since the portion with the serial number was gone it got a state assigned serial number.