Weight is the killer, more so than the 6' bed for a slide in.
As this is public forum, I will discuss legal, not possible:
My Ranger is 4x4 S/C with Payload Package 2, so GVWR of 5,140lbs (max for any '99 Ranger). I should have 1,500 lb payload. But I have some options: 4.0/Auto/8.8 adds 100 lbs, AC & 31x10.5R15s increase weight by 100lbs, and rear doors on cab another 100lbs, full tank of fuel is 100 lbs and Ford seems to have been a little optimistic on base truck weight. Then you add me and missus, some crap in box (toolbox and air compressor were there when I stopped at scales), and available payload was 800 lbs. (Payload package 1, which most Rangers have, starts at about 300lbs less).
Then my Adventurer 76R camper has a brochure weight of 1166 lbs. But:
The brochure weight, again is a mythical number - It didn't include jacks to get camper on/off (130 lbs) , tie downs, propane cylinder and propane (40 lbs), battery in camper (70 lbs)*, pots & pans, BEvERageS in fridge, clothes, etc. The real weight of camper loaded and ready to roll was a shade over 1,500 lbs.
Which put me about 700 lbs overweight. I can bring the camper close to legal, by removing all the options/personal items. And if I leave the significant other, tailgate, spare, trailer hitch and junk from box behind, replace the tires with the 225/55R16s from my son's Mustang, when I hit the scales with the gas gauge on empty, I would have been within spitting distance of weight. But that isn't very useful.
Also, for what I use the camper for, not having "facilities" was a major drawback...
I am on the hunt for a baby 5th wheel - Scamp's 19' or equivalent; 2400lb/400lb plus 500lbs for batteries/propane/pot & pans/BEvERageS/clothes, etc based on others real world numbers. A 3k lb trailer is still well within OEM limits.
*Pet peeve - propane cylinder(s) <empty> and battery are supposedly standard features, but the "dry" weight in brochure doesn't include them. IMNSHO, the standard features should be include "dry" weight. Adding options (dual tanks, dual batteries) <And delete the standard is an option> will change the numbers but so do all the other options (furnace, hot water heater, lights, etc). There is about 200lbs between jacks, propane tank <empty> and batteries that should be included in brochure weight for my Adventurer 76R (and over 100 lbs for the pop up campers mentioned above). The historic truck payloads were almost as bad - empty tank and no driver. At least the current rating system requires 150lb driver and 80% full fuel tank...