The 8 and 10 speed auto trannies are the game changer for gas engines. The 8.1 in my old Suburban needed to drop from OD into 3rd on any incline, but if you anticipated the hill and got it to 3200 rpm (peak torque for that motor) it would pull up almost any hill at almost any speed. If you dead-legged it and waited it for it to downshift as speed decreased, it could never catch up and it was a struggle to get up the hill. That was with only 340 hp.
An 11k trailer is no lightweight, even though it's 2k lighter than your old one...
I don't really need a diesel with for the weight I'm carrying but try and find a used 3500 without one...
