I am running the 285/70R17 Cooper Discover AT3's... I can't weigh in on the 70 vs 75 aspect ratio as when I was looking there seemed to be very few options in a 75 aspect ratio 285 tire for 17" rims.
The Cooper AT3's have been awesome...There is my 2nd set now on different trucks.. Last set was on my Chebby and they wore awesome. Traded that truck in with about 35k on the tires and they still looked almost new. On the cummins, I expect them to wear alittle faster due to the weight, but so far they have been incredible traction wise. I do regularly pull a 7-9k lb camper with this truck... OD is alittle tall with the 285's, but it does fine in my 48RE equipped truck with 3.73's.
The Cooper AT3's have been awesome...There is my 2nd set now on different trucks.. Last set was on my Chebby and they wore awesome. Traded that truck in with about 35k on the tires and they still looked almost new. On the cummins, I expect them to wear alittle faster due to the weight, but so far they have been incredible traction wise. I do regularly pull a 7-9k lb camper with this truck... OD is alittle tall with the 285's, but it does fine in my 48RE equipped truck with 3.73's.