yeah the 285 will fit stock rim without a problem

 

My 99 2500 has 16x6.5 and i always put 285's on. I've had the truck 10 years and have replaced the tires at least 5 times. They will fit but they crown cause the rim is too narrow and the center of the tire wears premature. I get maybe 40 k to a set of tires. I've had Good Year, Michelin ,Cooper, BF'S, Yokohams and they all did it. If you want to get the most out of them. Get the proper rim. They do look good though.

 

This senario has been talked about many time. From my own experience a tire much wider than the rim requires much lower air pressure to get even pressure across the tread. I'm currently running 315's on 8'' rims I have to run about 16 lbs psi to get even tire wear.This allows for a softer ride at the expense of handling.This is how they run them at baja to protect the sidewalls with the wide tread, I often wonder how they find the handling .no doubt they run much higher air pressures.Most combos from the factory have the tread the same width as the rim.