The tailgate narrowing happened in the late '80 to '90s. They were all 65" but shrank to about 60".
Chevy started it in '88 ('92 for the crew cabs) when their new body style replaced the old "square body".
With Ford, the '97s were the last of the wide style.
Dodge replaced their square trucks in 1994 when the big-rig styled Ram came out.
In general, campers built in 1988 or later are designed to fit the narrower tailgate trucks.
Older ones can be modified to fit, sometimes easily. You just need a few inches where it kicks out inside the bed behind the wheel well, if it does that at all. In my case, I had to section a piece of the shower enclosure and fiberglass it back together.
Height is easy, you just put something under it. I like using 4'x8' rigid foam insulation panels. They weigh almost nothing and you can glue them to the bottom of the camper and not have to think about them.
2017 Northern Lite 10-2 EX CD SE
99 Ram 4x4 Dually Cummins
A whole lot more fuel, a whole lot more boost.
4.10 gears, Gear Vendors overdrive, exhaust brake
Built auto, triple disc, billet shafts.
Kelderman Air Ride, Helwig sway bar.