Actually you can put huge discs on earlier model trucks, you're not limited to drums.
You just have to run 19.5 wheels. You can even run 22.5 semi truck wheels if you want, the hub adapters are about $1000. But the original brakes on even an earlier one-ton are perfectly fine. You shouldn't go down mountain passes riding the brakes anyway.
The problem with that truck/camper combo you drove was being single-rear-wheel.
I've owned several different single rear wheel trucks and several duallies. It doesn't matter what you do to a single-rear truck, it's never going to have the confident, stable handling with a camper that a dually has.
Skip the expensive learning curve others have done, get a dually. It's the only right way to haul a big camper.
Single rear wheel trucks can haul big campers "adequately". But not as well as duallies. If camper carrying is the truck's main purpose, why would you even look at singles? That makes no sense at all.